When I read what you wrote about your boyfriend, I felt compelled to share my own story.
I'm 25 years old, and I've been married (happily) to my husband, for the past 6 years. When we met, I was 19 and he was 23. As far as our sexual pasts were concerned.. I was a lot more "expienced" than he was. I felt it was important to be very upfront with him, about everything.. incase it changed how he felt about me, and about our replationship.
See, before I met my husband.. I had been with a LOT of guys (whereas he had only been with one woman before me). Most of them weren't even people I was in a relationship with. I just honestly didn't care, and I would sleep with whoever. There were rarely ever any emotions involved (on my end). I used to even brag about it to my friends, as if it were something to be proud of.
When I met my husband, I realized how wrong I was. I was ashamed of my past, and I wanted to badly to erase it. I could have just kept silent, and not said anything about it to him.. but I felt that would have been wrong of me to do. He was a part of my life now, and he had the right to know about those things. So, I told him.. and to my amazement, he was more than understanding. He was so accepting. He simply told me that my past was my past, and he didn't care about that.. and that he loved me. That was almost 7 years ago, and he still has that same feeling when it comes to my past. As far as he's concerned, it doesn't even exist. He knew about my past from the beginning, but he chose to accept me completely.. and he always has. He has never held my past against me, nor has he ever let it affect his love and trust in me.
Of course, when we met (and sometimes, still today) there were people who I actually thought were my friends.. who tried to discourage him from being with me. They tried to tell him what kind of person I was, and what I had done.. in an attempt to get him to walk away from me. But, it didn't work. Little did they know, he already knew those things, but he wasn't going to let my past determine our future together.
So, the best advice I can give you.. is to first, talk with your boyfriend, about everything. I don't mean the dirty details or anything.. but you need to be able to know for sure if that's all in his past, of if it's still a part of who he is today. Have that talk with him, and let him tell you anything he feels you should know. If you love him, and you trust him.. do yourself a favor, and let his past go, and just focus on your future together.
I want you to know that I'm here if you ever need someone to talk to.