Have you talked to him about how you feel? What did he say?
I don’t want to be totally discouraging. I do know one or two couples who started dating pretty young (22-23) and who did long-distance shortly after meeting who are still together a decade later. But, I think it will be an uphill battle.
FWIW, the few times I have thought past boyfriends might be cheating on me, I was spot on. I’ve definitely had my moments of jealousy or insecurity, but I don’t think either describe me as a person, so I trust my gut to tell me when something is amiss. I’m not saying your boyfriend is cheating on you — I don’t know — but I do think there’s something to be said about listening to your gut. What you feel might be one way to know that this relationship is not the right fit for you.