Lack of trust// need help💔

So me and my boyfriend don't live together (too young to move in together in my opinion) and I seem to never have trust in him! I'm always hearing rumours about him and another girl (nothing like sex) but talking dirty to her or wanting to meet her! He denies everything I ever hear and seems to always have an upfront story behind it that he says is the truth? But why don't I ever believe him? Recently he asked for another girls snapchat for his "mate" I seem to think it was an excuse to have it himself? I always see messages of girls talking to him or trying to! I want to trust him but I can't... I love him too much to let him go and it's hard to bring up the subject because all he does is get mad! Somebody please help its breaking my heart😭💔