Help!

Okay so I have been cheated on my the very few boyfriends I have had, and my mom was a very ‘strict’, controlling, always yelling, and long story short we don’t have a good relationship and so that kinda adds to my trust issues because the one person not suppose to leave left, and I can’t believe that anyone will stay, so I feel as though I treat my boyfriend a little bit like my mom treated me, and I’m so scared of losing him but I cant help but work my self up thinking he’s going to cheat or leave and so I get mad when he is even friendly with another girl and it causes problems because he doesn’t want to shut out that whole gender and don’t get me wrong I do believe him every time I trust that he doesn’t we’ve been together 3 years and we’ve lived together since I was 17, and I honestly know that he’s not cheating but I still get a whole scenario worked out in my head and it eats at me until I start something and I really want to stop but I don’t know how, please help!! How do I unlearn these? 😩