I really need help with jealousy. Any one that can help!?

I'm struggling really hard with relationship obsessions. Do I really love my partner? How can I know? Am I really just faking it? That kind of thing. It's making my life and relationship a lot harder than they need to be. I could use a few helpful coping mechanisms, trying to move away from less helpful ones like chasing reassurance.

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?

For some reason, my brain gets upset when my boyfriend hangs out with other people. I know I shouldn’t feel this way, but sometimes I can’t help it. I understand that he has a life outside of our relationship, and that’s great. He reassures me all the time, in fact, he often tells me he would rather spend time with me than with his friends. He’s a perfect partner, and I love him more than anything. However, I don’t want this to become an issue in our relationship. I know why my mind thinks this way, even though I don’t believe it to be true. My brain keeps telling me that he would rather be somewhere else than with me. Those words repeat in my head every time he’s out with friends, and I don’t know why. I want to find a solution to this obsessive and jealous thought so that I don’t ruin his time with friends. I really need help with this issue.❤️