It’s possible that your sexual orientation is toward women, not men. Unfortunately, I don’t know how to advise you as I don’t know enough about the cultural attitude toward homosexuality where you live. Here’s the link to the Wikipedia page on homosexuality in India: http://en.wikipedia.org/wiki/Homosexuality_in_India. It seems that times are changing, but slowly.
I do know that if you are so deeply attracted to this girl, it’s going to be very difficult to be intimate with your soon-to-be husband. That might be unfair to both of you. I hope there is someone you trust who can help you decide what to do. If there is a gay-friendly therapist in your city, you might find it helpful to make an appointment to talk through your options.
I wish you well.