I (24F) need to get rid of the obsession with my bf’s (25M) ex gf

I (24F) have been dating my bf (25M) for about 6 months. We are currently in a long distance relationship. I like to think that we are compatible and have good communication. The thing is that I know more than I would like to know about his ex. For context, this is my first relationship.

These are the thoughts I've had that I cannot stop:

\\- They dated on and off for about four years. That is a long time of shared history, and the on and off makes me insecure because they had such a deep attachment that they couldn't let go of each other.

\\- He told me he had hooked up with his ex a week before we started talking. At the moment, there was a misunderstanding as I thought they had just met up for closure. I did not know they had sex at his apartment. I then lost my virginity in that same bed, and now I feel like it was not special because she was there first.

\\- She was really close to his family and is still close with his childhood friends. I feel bad because I haven't been able to form a close bond with any of his loved ones.

\\- They lived togethvder for a totval of a year, and even lived in his parents' house for a few months. She texted him when we were already together (after they had hooked up) to let him know that she was moving in to his city. He responded with something silly, and then left her on delivered. I asked him if he ever thinks about her moving to his city, and he said he does sometimes. He also said that she does not have instagram anymore. (this is when my obsessive behavior started). I ended up finding out that she had blocked me and him. But if he noticed that she did not have insta anymore, it means that he checked. (this happened earlier in the relationship when we were not long distance)

\\- I asked my bf if he would do one particular sexual act, and he said he has done it. This act is something that I wouldn't feel comfortable doing. I know that I dont have to do anything I dont want, but he seems to enjoy it and I can't help but think they're more compatible sexually. I also found out through him that he had sex with her while someone else was in the room, and my immediate thought was "they were so desperate for each other".

\\- His best friend accidentally called me by her name once. He did not mean it maliciously, but it made me feel like Im just replacing someone in his life. Like it's not my place to be.

\\- His private instagram has pics of her. He doesn't really use instagram, and Im the only person that follows his account. He also has a picture that she took of him as his profile pic on his main account.

\\- He explained to me that he has felt different kinds of love- compassionate and passionate. He has felt passionate love with several people, but compassionate love only with his ex. This was when we had only been dating for 1 month, now im constantly wondering if Ive achieved the compassionate love title.

\\- When we started dating, he started doing a very specific affectionate gesture to me. I thought it was going to be our special thing, but then he stopped doing it because he said it was something he did with her and he wanted us to have our own special thing. While it was nice of him to stop, it made me feel like a replacement again.

I do not think my bf would ever cheat on me. This post is more about how to deal with this painful comparison and obsession. Every time we have a minor issue, I think about if he wished it had worked out with her.
How do I stop treating her like a competitor? How do I accept that he could have loved someone else, but loves me now? How do I stop needing reassurance to be at peace? How do I know when something is not anxiety and is an actual problem? How can I stop replaying imaginary scenarios in my head about them being happy together? Please help