self conscious

SO. This may sound completely ridiculous but I've been in a relationship for the past 5 months with this absolutely incredible guy that I completely adore. We're so alike and get on so well and I can see a long future with him.. BUT, before we got together he went through a stage of sleeping with A LOT of girls. He got and still gets a lot of female attention as he's a very attractive guy and all of it makes me so self conscious. I get jealous so easily and constantly think about his past experiences with other women.. I don't want this to get in the way of it our relationship but sometimes I can't help but bring it up with him and it puts me into a terrible mood.. any advice girls?? HELP