The five painful reasons men betray you and why it doesn't have to kill your relationship, by a marital therapist of 30 years who's saved hundreds of couples

You'd think if someone was caught having an affair they'd make a full confession. You'd think they would know if they wanted to stay or leave.

You'd think they would be able to explain why they were unfaithful. You'd think that if they promised to 'fight' for their marriage that their actions would match their words.

However, for lots of people recovery is not so straightforward and takes far longer than they would have imagined on discovery day. Sometimes the person who has been unfaithful vows to do 'anything' to make it better, but the next day sabotages everything.

Andrew G. Marshall, above, has spent more than 30 years working with couples in crisis, especially through cheating

Sometimes the discoverer of the infidelity is besieged by horrible images or overcome with anxiety - even though they want to move forward. Sometimes the betrayal has been so great - multiple affairs, illicit dating sites, prostitutes or cheating with a friend - that recovery is much harder.

If you can't get over your partner's affair, it is easy to think the pain is too great and you need to split up. However, I've spent  more than 30 years working with couples in crisis and have a message of hope.

It's not that there's something fundamentally wrong with your marriage, but you have been so profoundly hurt that you need extra help and to learn special skills to find a way through.

Trust me, I've witnessed how bad a marriage can get. Take the wife who came to me when she discovered at eight months' pregnant that her husband was addicted to internet porn and was having countless one-night stands with women he met online. Or the man who overheard his wife having graphic phone sex.

I've also helped a woman who realised her successful businessman husband was having flings in every country he visited for work. He even missed one son's graduation and another's 21st birthday party to be with his Thai lover.

And these aren't Jeremy Kyle types. These are the kind of couples you'd meet at a dinner party or your child's parents' evening. They seem, to all intents and purposes, just like you and me.

He claims couples who've struggled with cheating have a ray of hope in reconciliation - if they follow his advice

I think we're living in an age when infidelity has never been easier to commit or harder to deal with. I believe this phenomenon, which I will be exploring in this first part of an exclusive new series, has three basic causes.

First, is the role of the internet. There are countless websites and apps that exist solely to facilitate 'easy' sex. While it was previously unusual for someone to be cheating with multiple partners, for example, I'm afraid today it is only too common.

And the services of prostitutes are often just a click away, thanks to widely used pornography websites that carry adverts for sex workers.

It's also true to say that the most unlikely of people are able to use the internet to explore their secret sexual peccadilloes in a way they never could before. There's no fantasy too sordid for the online world. And it's only getting worse.

But there are deeper causes for extreme betrayal than the mere easy access that the internet offers. All too often, I find that many of the clients who come to me on the brink of splitting up have had troubled childhoods and come from fractured families.

Chaos breeds chaos - and my clients or their partners are often merely replicating the same break-ups and betrayals that characterised their childhood.

Another simple phenomenon making modern infidelity harder to deal with is this: men and women are much more likely to be friends today.

This was something that was much rarer 30 years ago when I started out as a marital therapist. Many of my clients tell me their husband or wife thinks it's acceptable to stay in touch with a lover when their fling is over. They're 'friends' after all.

In my experience, this only leads to yet more heartbreak, as the affair constantly reignites or threatens to, causing a great deal of anguish. Being betrayed is bad enough, but being betrayed twice in exactly the same way with the same person is twisting the knife in the most brutal way.

Here, I set out the most painful forms of betrayal I've encountered - and reveal the underlying reasons behind them...

HE'S CHEATED WITH YOUR BEST FRIEND

This is one of the most hurtful acts of infidelity. After all, the two people you trust the most are your partner and your best friend. The sense of violation can be overwhelming. This was the case for Julia, who sought my help after discovering her husband had a two-year affair with her friend.

To make matters worse, during this time, the couple were also trying to adopt a child.

Julia's friend was privy to the most private details of her marriage - for example, when she rowed with her husband or when things became tough because of the adoption.

And Julia was so close to her friend that, when the adoption was finally successful, the woman joined her and her husband and new daughter on a celebratory family holiday.

Unsurprisingly, Julia was devastated when she eventually discovered this extreme betrayal.

Andrew says that many men fall out of love and in most cases, it's because they don't feel loved themselves

Another woman, Allison, told me how she discovered her husband was cheating with a close friend of hers. Listening to a little voice inside her head, she checked his most recent phone bill and found that he had been in touch with her friend.

When she tracked back through his bills, she saw their flirtations had started two years before.

In the previous month alone, there were more than 1,700 texts to the friend and numerous calls.

Such extreme betrayal can make your husband or wife seem like a stranger. So let's start by asking, what kind of people have affairs? Well, they're often people pleasers, who want to be liked and make other people happy. Eventually, though, their needs and desires clash with that of their partners.

Normally people pleasers quash these desires, telling themselves 'my needs don't matter'. But then they snap. 'What about me?' they ask. 'Don't I deserve this?'

It's at this point people pleasers turn 180 degrees and become selfish. And it's then that the temptation to have an affair creeps in.

The warning sign for couples then is to spot when your needs and desires are diverging. When there is a clash, talk. It could save heartbreak.

It's not always possible to spot the signs, though, especially if communication is poor. Unfortunately, lots of couples imagine they 'know' their partner inside out. Instead, genuine interchange is reduced to giving or receiving instructions from each other. It's easy, then, to dismiss someone's feelings when all you do is give each other orders.

Into this crevice comes temptation. And unfortunately, people tend to fall in love with someone with whom they have repeated exposure - often from work or a circle of friends.

You'd think lovers would realise they were crossing a boundary and step back, but there are so many unhelpful myths that facilitate affairs.

For example, 'love will find a way' (and no one will really be hurt) and 'this is bigger than both of us' (so we don't have to take responsibility).

So if you discover your husband or wife has cheated with your best friend, bear in mind the potency of these myths. Don't be too self-critical.

However, what you mustn't do is descend into dramatics, either. When the infidelity involves someone you know well, the tragedy moves up a couple of notches. Instead of telling other friends or family about the infidelity, venting your emotion, why not pour your feelings into a diary? That way events are less likely to descend into a drama.

Keep talking - and decide whether you can restore your love for each other.

As for your friend, I would cut her out instantly, especially if she is a single mum. It might sound horrible to say, but nine times out of ten, single mothers just want your husband.

WHY HE HAS SEX FANTASIES

Judith sought my help when her partner of many years begged her to try swinging.

She was disgusted - and wondered why this desire had suddenly bubbled to the surface after so many years.

Yes, he'd always had a higher sex drive, but why the sudden need to involve other people?

So why are so many men obsessed with fantasy sex? You're going to be surprised at what I'm going to write next, but it's probably got nothing to do with sex at all.

Andrew also claims that a woman who embarks on an affair does so not out of lust or desire, but because she has a problem with her marriage. He encourages worried men to look at their own behaviour towards their wife

The reason so many men entertain such fantasies is relatively simple: boys are not encouraged to express their feelings, but to suppress them. Obviously, these feelings don't just disappear. They pop up somewhere else. Where? The bedroom.

It's because society has told us that the only time it's acceptable for men to express their feelings is when they're having sex.

This is the real reason men's emotional problems are so closely linked with their libido.

I told Judith her partner could try swinging with 400 women and an elephant and I still think he would feel dissatisfied because he wasn't addressing his emotional problems. She needed to encourage him to discover what these were, rather than obsess over his libidinous urges.

HAVING CHILDREN MADE HIM CHEAT

The story of one of my clients, Jill, perhaps shows the most common cause for men straying. In a word: children.

Jill told me her husband had cheated on her. And the first thing she told me that illustrate what kind of relationship they had was the following: 'We have four beautiful daughters.'

I told Jill she needed to realise why men fall out of love. In most cases, it's because they don't feel loved themselves.

Yes, yes, Jill said, but I did love him and everything was fine.

Really? Because all too often, I can see that men like Jill's husband feel their wives 'leave' the relationship first.

This was a shock for the blamelessly monogamous Jill. But as I explained, lots of women become so wrapped up in their children that they neglect their husbands.

I've lost count of the men who tell me 'she was too good a mother and not a good wife'. And so, every time someone talks about their 'beautiful' children, my alarm bells go off because it sounds like the children have been put centre stage, and not just adored but idolised. Not even the most doting dad will be able to cope with being a bit part in his own marriage for long.

Many men just want to please their partner and so don't rock the boat — even when they're unhappy with the attention they receive from their wives.

But these are the men who will use affairs to jolt themselves out of their numbness. It is a warning to devoted mothers.

HE STRAYS WHEN SHE'S PREGNANT

Cheating on a wife who is pregnant or has recently given birth is one of the last remaining sexual taboos. But there are good psychological reasons behind such a destructive act.

When men cheat during their partner's pregnancy or just after she's given birth, it is a clear signal they are uncomfortable about becoming a father.

Sometimes it triggers a crisis about their own father, especially if they are frightened of becoming like him. It can also lead to feelings of entrapment and claustrophobia.

Many men tell me they become frozen with fear by their new responsibilities. 'How on earth am I going to support all these people?' they wonder. This can be a huge issue if you hate your job and dream of escaping.

Some men aren't tempted to cheat during their wife's first pregnancy - but the second can tip them over the edge.

Why? Many men find fatherhood and the reality of childcare such a shock that they fear the second baby will only make matters worse - only this time they'll be pushed further down the list of their wife's priorities.

I Can't Get Over My Partner's Affair by Andrew G. Marshall, Marshall Method Publishing

Sex, already an infrequent event because of the pressures of baby number one, will surely only become even rarer when baby number two arrives.

It's a biological fact that young children kill a couple's sex life. For the first 18 months after a baby is born, all the oxytocin - the bonding hormone - goes into the relationship between mother and child.

And, let's not forget, as we've already discussed, men need sex because it is the one way it is socially acceptable for them to get close to someone.

Into this mix, it's hardly surprising that the escapism of a fling is so tempting to many new fathers.

A word of reassurance, however: couples with children are more likely to survive an affair than those without. Children force us to find a balance between satisfying individual short-term goals and considering others and the greater good.

WIVES WHO TEASE OTHER MEN

Craig was another of my clients who sought my help. While his wife hadn't yet had an affair, she was in contact with her ex after a turbulent time in their marriage. Craig was convinced this was dangerous.

His frustration bubbled to the surface and he asked why she was deliberately contacting her ex when, as he put: 'We have so many other problems to solve.'

Well, I had bad news for Craig. Women normally only allow other men to chat them up if they're feeling lonely, desperate and sad. Did he really listen to his wife, I asked. Did he find himself pushing her away rather than truly interacting with her?

Too often, a woman embarks on an affair not out of lust or desire, but because she has a problem with her marriage.

The men she seeks are just a symptom of the problem and the problem is usually something her husband has been doing wrong.

Names have been changed.

A version of this article, part of the Femail Classics series, was originally published on November 18, 2015.  

Adapted from I Can't Get Over My Partner's Affair by Andrew G. Marshall (Marshall Method Publishing). Andrew G Marshall’s new course, ‘My Best Relationship Tools’, is available at courses.andrewgmarshall.com/relationship-tools