I wouldn't let my mum into the appointment if I were you. Mothers can reconstruct your childhood in ways that they would like to remember when you're sitting there remembering thinking you were a boy and playing with cap guns, they'll be remembering you in a pink frilly dress, never mind that you bit your mother in the fight to avoid wearing it.
And yeah, I reiterate what the others have said. Just tell hiim what you feel. He'll ask questions about various times in your life and tell him as best as you remember. It's not something to try and manipulate. If you are TS, it will show up. If you aren't, can you imagine how you might feel a few years after a wrong diagnosis when you have a goatee and hairy back?
There's a guy in Australia who's suing his doctors because they approved him after he manipulated them deliberately. He presented as MtF, got tested, failed, read up on how to manipulate the diagnosis, went back and was approved for hormones and surgery. A couple of years later, he's regretting it and blaming his doctors. Never mind what that says for taking responsibility for your own actions, the point is, let the professionals do their work and make the diagnosis.
Dennis