What if I have been with my boyfriend for 7years and still cant trust him?

I have been with my guy for 7yrs and thing are not so great. When we first dated he use to be jealous and very clingy not it feels like he can’t wait to get away from me. This started when I broke up with him a year ago the went back after him when I relized I loved him still he wanted nothing to do with me. I knew he had a girl in his life but that they weren’t dating, they were co-workers. They hung out slot and talked slot well he finaly allowed me back in his life he says we are working on things but I don’t see changes it’s been four months and he doesn’t want to call me his girlfriend. He has gone out with this girl behind my back when I ask about it he gets mad he says there were other people there but I don’t know if I should believe him he lies in the first the place I alway acuss him of cheating in me with that girl and sometimes others he says he can’t take it at times but it’s his lies that cause it. I don’t know what to do I want to trust him I just feel like he will cheat on me like this girl might be so much better that’s why he goes behind my back to see her and talk to her he say there just friends what should I do am I acusing to much is that what’s pushing him away and maybe in to her arms what does she have that I don’t what do I do??? Help if you can thanks