Has anyone overcome Retroactive Jealousy? It’s ruining my life and hurting my relationship

I'm 18, and been in a relationship with my man for nearly 2 years. I started living with him around 2 months ago, and all I do is think about if he's cheating. We were long distance for a year and a half of our relationship, maybe seeing eachother once every month or two. I decided to move in with him, and ever since all I can think about is if he's cheating or watching porn. When he's in another room I think he's doing something wrong, I have to check on him every ten minutes to ease my anxiety. I didn't have this problem before moving in. Granted he has talked to some girls on his phone, even having his ex on his phone (didn't do anything bad) and he is porn addicted though he is getting better for me. It's gotten so bad I want to leave him. A couple days ago I broke up with him and it absolutely broke my heart, I couldn't bare it so I gave him a month to show me he can do better, and for me to work on myself. If I'm still unhappy with us I'm going to leave. I love this boy more than anything. I'm scared to be without him, this is my first real relationship. At this point I refuse to even sleep until he is sleeping. I don't want to start over, I don't want to leave him, but I really can't take this pain it's causing me. It's all I think about. I've convinced myself so many times that he's cheating, but I know he wouldn't. I question whether it's anxiety or intuition. Maybe I just know deep down he really is cheating and I just don't want to believe it. I don't know. I don't think he would do that, but at the same time he's really into women. I hate that he looks at other girls in a sexual way, it bothers me so much, and we talk about it often, but with it being an addiction it's difficult. He has gotten a lot better since we have talked about it. He understands I have an issue and is usually happy to talk about it over and over and promise me over and over that he's not cheating. He allows me to have his phone whenever I want and everything, I have no reason to think he's cheating, but I can't get over it. It's not fair to him either. How do I deal with this? How do I stop hurting so much?

What do yall do when yall think of past partners or other people during intercourse with your current partner. I ended up confessing that to my partner and it’s damaging the relationship or making things really difficult. Having a really hard time trying to control the thoughts. I even think of other people while with my partner. Any advice or anyone with similar experience?? Please

I’m gonna try to make this make sense, and any support or advice would be great. I have a beautiful girlfriend, who I’ve been dating off and on for a year. We were really rocky but got our shit figured out 4 months ago and have been strong since. I truly love this girl more than I’ve loved anyone. And I know based off the sheer amount of ocd that has come up on our relationship, that she means a lot to me. Me and her were in a friend group in 2022 and we never liked each other. However she had a sexual relationship with one of my old friends. Fast forward to now I haven’t talked to him in a long time and I don’t see it as an issue. However… I keep having this vivid flashback to him touching her some kinda way in 2022. I can’t remember exactly what happened or the details but it’s running through my head. I guess this is retroactive jealousy but it’s really almost hurting my feelings. I wish it would stop but I know ocd doesn’t work that way. I just wanna be happy with my girl and not upset at her past experiences