Do you want to be in a relationship? or relationship with sex? or friendship with the opposite sex?
If you want to be in a relationship, then just tell her, there's no point in delaying such things. If she says yes good for you, if not, forget her or settle for being friends.
I know how you feel, i've been there and it's a wonderful feeling. You just have to be confident is all. oh and don't forget, good hygene is important to women, they love clean guys most of the time