Mmm. This is interesting.
I mean, I respect religious rules. But I see no justification for the belief in no contraception, in fact, I think that no contraception is a theoretically bad idea.
Also, it doesn't say in the Bible to not have sex before marriage, and in fact, marriage meant something completly different when the Bible was supposedly written.
About you - I'd say, do what feels right.
You think it feels rihgt, you love her, and you feel more than comfortable with it.
Think about what would be right for you. Morals and principles can change through life, as you grow up and as your circumstances change. And I'm sure that God can understand how things can change, how circumstances change.
Plus, love is one of the things that is really promoted (for want of a better word!) in the Bible, it comes above all others.
Just do what you feel is right, I say. x