How to put HIS past away from ruining your present?

I have big issue with living with my boyfriends past. I mean he is way older then i am so no ahem he have more experience. But it bothers me so much. I keep tryin to find some things on him to prove myself that he is cheating because of his past. He is into model type of chick and even though he is the one who went after me if i try to compare myself to one of them i lose all self esteem like i am nothing. He had some busted ones too but who cares because i daymn sure aint better looking then one of them beautiful model chicks he had at some point. I keep gettin my jealousy and self esteem break everything i had with this man, but i have no control over it. What should i do? Can i somehow stop this? It is killing me and i can tell its killing him too. Help!