How dare you shame him for his sexual past. He deserves someone who is responsive to her own feelings for him and not judgemental over something entirely reasonable he once did. Buck your ideas up missy, the relationship isn't all about you and what you want your fairytale boyfriend to be.
I am also bisexual with heavy preference for girls, but I, like him, experimented with male friends when younger partly because, I feel, we had no access to women. It isn't really something women, who are objects of desire from the first, can comprehend, but it's up to you to try.
You will note that I am now entering my sixth year with my girlfriend.