But... do you have to get people to believe you? If you tell them, and they listen, then that's where your responsibilty should end, surely. Once they have the information then it's up to them what they do with it. Whether they believe you or not doesn't change who you are. The only people it seems you have to prove yourself to are those in a position to give you the means to progress in your transition. Everyone else... *shrugs* GID isn't like Fantasia in The Neverending Story, it doesn't suddenly disappear if people don't believe in it.
The overriding concern, in my view, is: do you believe you? If so, let other people think what they like. 🙂