Hi Carbon,
I phoned my GP receptionist that I am making an appointment re my gender, so my GP knew what I was coming to discuss. Docs seem to only have a short period of time for you, I was hoping for 20min. but I had to almost point form articulate from my teens to 70 how I got to believing I am trans. I have discussed with my cd & trans friends about my story enough that I am comfortable, not anxious, been out to my family so I just relaxed into the 12 minutes I had and was just me. She is a very caring and empathetic Doctor and immediately had me set up for blood tests and a pelvic ultrasound. The next day she had an appointment for an Endo a few months later.
So breathe, relax and be yourself. Docs are there to listen and help, they don't bite.
All the best in your journey.
Jamie