It's normal to be attracted to one gender more than the other.
I consider myself to be bisexual, I am definitely attracted to both men and women, but I'm definitely more attracted to women, and I've recently come to the conclusion that I don't think relationships with guys work for me. The idea of ending up with a guy has just become more and more weird feeling. I mean I truly loved my last boyfriend, but it always felt like there was something missing and sex just didn't feel that fun; breaking up with him was the best thing at the time, because we can continue to be friends without boyfriend/girlfriend relationship stuff getting in the way. I still love him, but as a friend and I don't regret breaking up with him at all.
Tbh, it sounds like you need to carefully consider where you stand with your boyfriend. Continuing on with him because you feel you've got to the stage where you're comitted and you feel like you 'can't' get out of it sounds like you're doing it for all the wrong reasons. Do you really want to end up with the both of you unhappy further down the line because you didn't break it off when you realised it might not be quite right? It's not fair on you, and it's not fair on him. Don't you think your boyfriend will be even more hurt if he finds out much later that you don't feel the same way he (presumably) feels about you and instead only loves him as a friend, than if you break up with him now?