AITA for constantly mentioning her?

To start, I’ve already broken up with him. I’m just a firm believer in not continuously mentioning something if you’ve forgiven it.

A month ago, I caught my ex texting another girl. He was planning on inviting her to a pool party his friend was hosting. When confronted, he said he was trying to “get her to talk to his friend” and “it wouldn’t make sense to invite her for himself if him & I were going together” and went as far as calling his friend to back him up and showing me their group chat. Bullshit, I didn’t believe it. And even if I did, I’d still be disgusted & disappointed that at our grown adult age, he feels the need to be a “middle man” for his friend to get women, especially if you’re already in a relationship. I stayed with him after the fact, stupidly, and noticed he was still following her whenever I used his Instagram. I asked him to unfollow or block her twice. The third time was last night when I actually got upset at this point because why the hell do I have to keep asking you to unfollow someone you basically cheated on me with? I broke it off then. I’m not insecure, im not the type to be upset over my man following women or liking their pics because it’s social media. But this is different. It’s disrespectful and disgusting.

He says I was looking for “any reason” to be mad at him and why im acting like this. I want women’s opinions. I already know how annoying it is to move on from something but the other person still brings it up so I know I should’ve left when it first happened.