Wendy,
You will almost certainly get caught, eventually. The longer that takes, the more hurtful the deception will be. Same goes for just coming out with it. It will always be more hurtful the longer you carry on the deception. IMO, if your "special someone" doesn't deserve to know about this part of you, then maybe she's not that special. Or maybe... you're not. Stop being ashamed of who you are.