His past..

Anyone else here have trouble getting over your bf's past? It's such a weird thought, but often times I can't help thinking about his past and things he's done with females before me. I was his first overall to actually have sex with, and he's my first too, which is great we have that connection and first time experience with each other. But it's just weird I can't help thinking about it sometimes was wondering if any of you have dealt with anything similar and how to overcome it?!