why am i jealous of my bf going out without me?

whenever my boyfriend goes out with his friends, without me i have a horrible feeling in my stomach and worry the entire night until he’s home, we’ve been together two years and he has cheated on me in the past before we were actually going out, i just worry he’s going to cheat on me again and try and talk him into seeing me instead of his friends and i just feel sick when he’s out with them and not me, whenever i go out with my friends without him he gets mad and refuses to talk to me until i’m home. i’m not breaking up with him, what do i do???