Lesbian with a boyfriend?

so I have had sex with girls and I know that I'm a lesbian, but there's this one guy that I really somehow am attracted to. (which leads me to believe I'm homoflexible) but I'm technically a virgin, and we've been together for about two months and we've gotten really close to having sex several times. we got /really/ close last night but I started to feel really really wrong and just bad about it so we stopped. part of me wants to do it just to know what it's like, but the other part wants to maintain my integrity as a proud lesbian. I'm also afraid I'm just using him to get what I want physically... is it worth it?