@ ukftminneed, If you were relaxed about coming out to the people you mentioned, this is no different, the medical profession is there to help in whatever issues you are experiencing. You believe you are transgender, well let your gp know when you first sensed this & whatever your learning experience is, if you cross dressed & when, tell your story (we all have one). This may not be your Doctors specialty & will probably refer you to a gender Doctor or a gender therapist. Your gp will send you to a lab for blood tests. I also had an abdominal ultra sound. Just be yourself & go with the flow.
Good luck.