help!!

whenever my boyfriend goes out i can’t stop worrying. i feel awful for not fully trusting him, he’s gotten with a few other girls in the past while we were still in the talking stage but we’ve been together for a solid two years now and he hasn’t done anything like that since, i have an awful feeling in my stomach all night until he gets home and i can finally relax, how do i stop this from happening, i just can’t stop worrying and it makes me feel horrible