Hey hun,
As Virginia Marie said, relax and take a deep breath.

And another one...
Feeling a wee bit better? (Even just a tiny bit?).

This *is* something that, when it becomes overwhelming, can be absolutely terrifying. I'm 22, and, from the sounds of it, am the exact opposite of you - while you're a genetic boy who's always felt like you should have been a girl and whose sexual feelings are as a woman (not
for a woman necessarily, but
being a woman), I'm a genetic girl and since I was very young yearned to wake up as a boy (still do, actually), and whose sexual feelings have always been as a gay man. Even if I do imagine being with a woman (rare, but it does happen

), I'm always always
always male. I cannot imagine myself being, and
do not want to be, a
girlfriend. Since a very young age, whenever I looked in the mirror (and still do, I've not transitioned or anything yet) I've always tried to see past the female exterior and see the man I am.
Sorry, long story short, yes, I understand, as will many people here, exactly where you're coming from and how you're feeling and the terror you must be experiencing right now. As hard as it may sound, the important thing is not to let it overwhelm you - instead of thinking about everything all at once, take it in small steps. You can't eat an elephant all in one go, but if you take one tiny bite at a time, you'll eventually get there.

By the sounds of it, the first thing I think you should do is find someone you can confide in, be they your mum or a counsellor at school or a best friend. Even calling a youth/GLBT helpline can help, and they'll be able to direct you to services in your area that can help you further. Or your doctor (sorry, don't know why I didn't think of that first

), doctors can be great helps too.
As for taking tiny steps towards transitioning, you'd have to talk to some MtFs, I have no idea about how you ladies go about it all, but again, small steps, do things that make you feel better in yourself but that won't necessarily get people cross-examining you as to why you got your hair cut like that or whatever.
Sorry, that's the best advice I can think of at the moment. But, again as Virginia Marie said, you've come to the right place.

Take it easy, hun. Don't panic, don't be scared to ask us advice if you need it, or questions about anything and everything, and don't let anyone tell you how you should live your life - no-one can live your life for you, and you can't live it to please anyone else. Stay safe, of course, but don't try and appease other people's happiness at the price of your own.
And, whatever you may think, or however you may feel, you're really not alone in this.
xox Will