obsessed with my boyfriends ex

so guys I think I am obsessed with my boyfriends ex. i am a freshman in college and he is a sophomore, basically one time we were talking about our body count and she was brought up. turns out he fucked her 4 times, and when they ended it was on her terms. every time I am with him or even if I’m not with him I’m obsessed with this girl, thinking about her and wondering if she’s better than me and hating her guts for the fact that she’s fucked the guy I’m in love with. I’ve already blocked her off of his phone but like I’m scared he’s going to see her in public and then like something will happen I don’t know about. pls help. also, he’s in a fraternity and her sorority and his frat do a lot of stuff together and I don’t want him go near her and I tell him not to go to the events and he doesn’t, but this Saturday there’s a party she might be at that he’s going to and he told me that if he saw her he would give her a HUG. idk what to do. literally crying typing this