If medicine is definately your calling, and you can't get any surgeries done by then, you could talk to your guidance counselor once you are accepted and ask to be allowed to pass. The other possibility is to wait a year, get started and then apply with your name and identity changed. Either way, it will be easier to have your proper gender and name on your graduation certificate and license when they are made then try and change them later.
Without knowing your parents, I can't really guide you very far with that except that its not worth losing your life over. Been there many times before I told my parents. Seeing a therapist and having some clout behind you never hurts, and they may know of a therapist that treats parents of transgender children. When I told my parents, it had come down to either they accepted it or I was checking out, and that is waiting way too long.
If the medical school requires all females to wear dresses, save yourself the trauma and do something before entering. Two years before I told my parents, I attended nursing school and wound up having to wear stockings, a dress and a little hat in clinics. That was only for a year, and believe me, you don't want that trauma.
There is no reason why you should have to be in a situation of desperation as you are. There are choices, and though none of them may look easy, do yourself a favor and tell someone, parents, therapist, someone who is there physically before you go down a road you will regret.
sam1234