i think i’m going crazy

My boyfriend and I have been fighting recently and it’s mostly because I am uncomfortable with him being friends with a certain girl. (He has multiple other girl friends that I love and don’t care that he’s friends with them.)

However, he’s gone on a date with this girl and openly told me that she cheats on her boyfriends and such.

I told him that I’m uncomfortable with their friendship and put that on him to decide what was best.

I think I don’t trust him because the other day I went through their texts and they were talking about mine and his sex life.

I confronted him about this and he didn’t think there was anything wrong with it.

He’s making me feel like the bad guy in this situation and I honestly don’t know what to do. Help