She slept with another guy in our break

We broke up a while back after a 3 year relationship where we went through a lot together and she started going out and drinking straight away basically any chance she got. She met a guy on a night out and kissed him.

Surprisingly I didn’t really care, considering this was 2 weeks after our breakup, I just thought “she’s trying to move on I’ll let her I guess” but then she meets another guy.

Someone I used to talk to and they also used to be friends years ago, anyways this was about a month and a half after our breakup.

Basically she went and slept with him twice but also started speaking to him for four months. This hurt bad. After everything we went through including the fact we almost had a child. We started seeing each other again and sleeping together, she thinks we have a chance but I don’t know if I’ll ever get it out of my head it angers me the thought that she didn’t care or even have a thought about us or what we went through.

I don’t know what to do at all because I know we love each other a lot or at least she acts like it and I don’t wanna lead her on at all but i feel like I NEED to make her understand but I just can’t and it pisses me right off. What the f*ck do I do???