Help?

So, long story here. My current boyfriend and I have been together for a year now. We previously dated in 2016 for two months, but broke up after I found out he cheated on me.

He’s slept with a lot of girls. Like, more than I can count on both my hands. I’ve only ever slept with him, and my ex boyfriend once. His past bothers me very much, and sometimes I feel like breaking down and crying because of it. Thoughts cross my mind, and I just feel as if I’m nothing but another chick to sleep with, and sometimes feel like a whore. Even though he assured me he loves me. I’ve just got a hard time dealing with the fact he’s slept with and had casual hook up. Is it just pure jealousy? Or is there something deeper than I can work through? Any advice and help would be greatly appreciated.