Insecurities

So I’ve had my insecurities since 8th grade (I’m entering senior year soon) and I just got into a relationship 3 months ago. My boyfriend has a bunch of pretty friends and he’s super attractive so I get insecure a lot and it causes us to argue cause I get jealous as well. Any advice to help overcome these insecurities because for all these years I’ve just put them in the back of my head but now that I’m with someone I’m scared of getting heartbroken. I haven’t been able to enjoy my relationship to the fullest cause of these insecurities and I OVERTHINK so much. I basically push myself away from him. It’s kind of that feeling where you just wanna isolate yourself and be alone. Also a feeling where I don’t wanna be in a relationship so I can stop worrying but I DO want to be in a relationship with him cause I love him to death and I know if we break up I’d be devastated. He’s super sweet and tries to bring me up but this is a personal problem. Any advice?