I can't come to terms with my boyfriend's past promiscuity! Help!!!?

A few months ago my first and only bf told me that he has a very promiscuous past. I feel very depressed about it. We've been together for a year, he's never had a girlfriend before, but engaged in unloving during his univesity years some years ago. He's 35 now (I'm 26) and we are planning to get married next year. However, his past haunts me and I couldn't feel worse about it. I come from quite a conservative family and haven't had yet. He doesn't pressure me and says he can wait as long as it takes. The problem is that I don't think I can ever have with him, I just feel utterly disgusted! I do love him, but his confession has really devastated me and I see him differently ever since. I can't take this anymore. We've been to counselling and even broke up but came back together because we do love each other and can't be apart for long... how can I accept his past? He says it's all in the past and it will never happen again. I know he loves me, but this is killing me slowly.