Amicable Exes?

I’m so curious as to how people have navigated their coparenting with partners amicably. I recognise it’s early days for myself and ex partner. He cheated while I was 8 months pregnant. It was the most traumatic thing I’ve ever experienced. We worked through things, at least I thought. I discovered him behaving inappropriately online again recently, and for me it just flipped a switch. I was so done. I wasn’t in love with him anymore, and even if I was, it made zero difference. The relationship was done.

I guess my situation is curious. Whilst I’m very hurt, I’m not struggling to maintain a relationship with my ex. I am positive and look forward to my future and meeting someone. Am I numb? Am I broken? Why doesn’t this feel harder? I have him round for dinner, we go out to things for our son together. I enjoy the companionship, but have no desire fix,repair,chase. I’m affectionate with him, we’ve even had sex since. It hasn’t changed my stance.

Please give me some insight to this. It feels strange.