'It was an ordinary evening at home, until one casual comment from my child unravelled my life.'

As told to Ann DeGrey.

When you've got three children under the age of three, your life is incredibly hectic. For me, it's been a constant blur of exhaustion and joy all mashed together. That's where Luke* and I were when Anita* came into our lives.

She was a live-in nanny from Norway, very sweet and kind. She was very patient and fun and the kids adored her instantly. She had a knack for making everything seem less hectic, and she just got on with helping with the kids as though it was easy. I couldn't really have coped without her.

Luke and I were juggling demanding jobs along with the tiring logistics of keeping three kids happy and fed. I wouldn't say we were fighting at all, but we weren't exactly connecting either. It was very much survival mode, both of us just doing our best to get through the early years.

Watch: Personal development coach Felicity Morgan shares her 60-second test to catch cheaters. Post continues below.

Anita helped keep us afloat because she was more than just a nanny, she was a lifesaver. She always got on very well with Luke, and he'd said many times, "What did we do without her?"

I never suspected a thing, not a thing.

And then one day, she left. It was very sudden; she explained that she wanted a change in career and was very sad to leave. I was devastated as I knew how hard it was to find someone as great as her.

She said she'd been thinking about it for a while, and although I was surprised, I didn't question it. I was too busy dealing with three upset kids and the pain of having to find a replacement.

But a few weeks after Anita left, Luke said he needed to talk. He was very calm and quite formal when he said he was unhappy and wanted to break up. He said he'd been struggling for a while, and that he needed to live on his own.

I was absolutely stunned and so very blindsided. I asked him if there was someone else, and he looked me straight in the eye and said no, that he just wanted to be single.

I had no reason to doubt him. It wasn't that I was being naive, but because it felt so out of nowhere. I thought it was probably just temporary, and we'd get back together soon.

In the next few weeks, the kids would go to Luke's place on weekends, and they seemed to adjust quite well. When they were with me, they asked about Daddy constantly. I kept explaining that he needed time to himself, and he loved us all. I still didn't think there was anything else going on.

Then one night, our five-year-old was playing with her toys and casually said, "Anita sleeps at Daddy's house now."

At first, I thought she was confused. I asked her what she meant, and she said, "She makes yummy chocolate pancakes there like she did here."

That was the moment my jaw just dropped; suddenly I put two and two together. He had left me for Anita… I called Luke and told him what our daughter had said, and he didn't deny it, he just said he needed to see me face to face.

I caught up with him, and he admitted it; yes, he and Anita were seeing each other. He said it had started "after" he moved out, but I wasn't an idiot.

Whether it started before or after he walked out doesn't really matter now. What matters is that he cheated on me and made me feel like our marriage had just quietly fallen apart when he'd been planting the seeds of a new life with our nanny.

I tried calling Anita, but she'd blocked my number. I wrote her a letter telling her I was devastated and thought she was pure evil. Of course, I never heard back.

I felt humiliated and completely betrayed. I trusted that woman with my little family, and she tore it apart. Yes, it takes two to tango, but there are plenty of fish in the sea; why did she have to go after Luke?

She was someone I trusted so much I'd let her move into our home. I wondered whether they'd had sex in our bedroom when I wasn't there, or whether they were just laughing at me behind my back.

It's been over a year now. We've worked out a custody arrangement where I have the kids most of the time, and they stay with their dads about 40 percent of the time. My friends say I should be pleased that the kids, at least, like her. But it has been soul-destroying for me.

Now I'm just focusing on putting my hurt aside and being the best mum I can be.

*Names have been changed for privacy reasons.

The author of this story is known to Mamamia but remained anonymous due to privacy.

Feature image: Getty. (Stock image for illustrative purposes).