Intrusive thoughts about my ex

I can’t stop with the sexual fantasies about my ex. I love my wife and our daughter, and I don’t want to fuck it up, but my ex is still a part of my life, and she consumes my thoughts. I can’t just cut her out, we coparent a kid.

It’s not like I’m regretting breaking it off. I had very good reasons to do so. And it’s not like I’m unhappy with my wife, she completes me.

But I can’t stop thinking about my ex. It got to the point where I made a pass at her the other weekend when we took our kid to a movie. She turned me down because she’s a decent person and I’m a piece of shit. Good for her. Then I thought “can I apologize and also parley this situation into sex?”

So that’s where I’m at. I’m basically a sex pest with a poker face, and I want to be better, but I don’t know how.

Anyone found a good way to be good?