'It was a great comeback line, but it ended my relationship.'

You’ll find it easy to judge me. You might say I shouldn’t have been in the relationship I was in, and that I’m a fool.

In many ways, you’ll be right.

I never expected to have an affair. He was married; we were together for five years. We met through work, and I think I saw more of him than his wife did. She was a lovely person. I often wondered how – or if – I reconciled the fact I was in love with her husband with my feelings about her.  I think the experts call it ‘cognitive dissonance’ – a feeling of discomfort that comes from holding conflicting beliefs or attitudes.

There were no children; he was adamant he didn’t want them, and she seemed in step with that. Plus, we were sleeping together so much it was easy to believe there were insufficient libidic leftovers for his wife to get much bedroom action at all. That gave me hope – I mean, if their relationship had dissipated from Big Love to friendship, it was surely just a tiny step to divorce. Wasn’t it?

The fight that spelled the beginning of the end wasn't one I saw coming. We'd fought before - ours was a tumultuous, passionate relationship of stupendous highs and heart-wracking lows. We'd spar over words and ideas, and make sarcastic remarks about staying or leaving a relationship, laugh until we wept about ideas for offbeat musicals or headlines. We'd talk and talk and talk. I was crazy about him.

Then came the day he arrived at my house, his face white, eyes bloodshot, tears blotching his skin.

She's pregnant, he said.

LIKE Debrief Daily on Facebook. 

My heart began to thump. Everything went very still. He sat down and sobbed. My whole body tingled, as if tiny ants were swarming randomly across it. I understood what people meant when they said their blood turned to sand.

Then I did something I still can't quite believe: I comforted him. I got water, a cool washer. We talked about what would happen and what we should do and how he didn't want the baby. And I babied him and believed him.

I didn't sleep that night. As the digital clock by my bed flashed mutely and ticked hour over hour, a question that started small began to balloon until I could think of nothing else.

And this is where you will think I'm the fool I very much turned out to be.

I had believed him when he said he didn't sleep with his wife. Yet here she was, pregnant. I knew in my heart he would be a father, no matter what he said.

We spoke on the phone about 11am the next day. His tears had stopped. Mine ached just below the surface. And finally I asked the question: How did she get pregnant?

I don't know.

You lied to me.

I didn't. I'd never lie to you.

Well, we seem to have here two mutually exclusive facts: she is pregnant but you haven't had sex with her. What was it - immaculate conception? Because we should call Channel Nine and sell the story.

He hung up.

An hour later he called back. The lies spilled so easily from him.

I was half-asleep, he said. I didn't even remember it had happened. It only happened once. She took herself off the Pill - I didn't know.

I love you.

I will never know how I found the words that came next. They roared from deep inside me, finally acknowledging that essentially, everything he'd said, all the love he'd professed was, in the end, bullshit. I didn't care that I was near a crowded market and that people might hear - god knows, I'd kept secrets enough. It was the rawest grief I've ever felt and every word felt like it wounded me more than him.

You are so full of shit, I screamed. You have lied and lied and told me you didn't want kids and now you've miraculously changed your mind. You knew I wanted children, and you let me think I would be with you and for me that was compensation enough for remaining childless. And you have taken the years that would have allowed me to have them. I HATE you.

I wish I could say I ended it there. We didn't. We stuttered along, pretending everything would go back to how it was, but of course it never did. It was a relationship in its death throes - we just didn't want to admit it.

I will never have another affair. I am single now, and astounded when I occasionally come across married men who openly flirt and suggest that given half a chance, they'd take it further.

But I will never forget the pain of that day, worse even than the day his child was born. And I will never go through it again.

Like this? Why not try ...

I was dumped by my friend, and I still don’t know why.

How – and why – to travel alone. (It’s not as scary as you think.)

‘Life’s too short for toxic friends. This is how I got rid of mine.’