Is it a matter of feeling like a fake, or fear of being seen as a fake? The two are a little different.
If it's fear of being seen as a fake, then the answer is pretty much a matter of getting yourself to the point where you really don't care how other people see you. It takes a while; it may help to know that most people really don't care, and even if they know, probably won't confront you or say anything about it. The point is that you know who you are, and the perception of others can't change that. You're not a fake, and the opinion of others doesn't cange that.
Actually, this applies to feeling like a fake, as well; part of that feeling is due to the conflict between who you are and society's expectations. If the feeling is really strong, it may be because you are unsure yourself of who you are; if you're not seeing a gender therapist, you probably should. Sometimes it's a lot easier to figure out who we are when someone else is asking the right questions. The only reason to feel like a fake is not being true to yourself.
Annie