Seriously, you're going to give up because of PROM? So what? You can't wear a dress. I think this is a good thing since you won't have that stigma attached as "the guy who wore a dress to prom." I'm sorry it is this way but it is and that's what peeps would have thought even where I'm from and I come from one of the bluest areas in the country. It's so blue you can't tell the social-demographics from the sky. Now, you can go to college, get on HRT and live your life. You should be thankful that torture that is High School is over, have a grad party, get a bunch of cash and use that to fund your transition. When I was your age, I couldn't go to prom because (A) I wasn't asked and I don't ask people out and (B) I had a serious heroin addiction and on the day prom was held I also discovered the joys of crack cocaine. This was the 1999-2000 so I had no Internet and nowhere to turn to regarding my lifelong transness. I realize the Intenent existed but by this time I was too wrapped up in being a criminal and drug addict and erstwhile prostitute (why? Because I liked to commit crimes while dressed like a woman and people told me too cause I looked so much like a chick).
So, I'm like LeStat in the Vampire Chronicles and I'm going to give you the choice I never had: do something. Now. Forget prom, it's like 4 hours of your life. It's nothing. And in the end, it's the little things that add up and make one feel or be a woman. So, I'd get started on that and stop worrying about prom.
Please dont take this as an invalidation of your feelings. I know at that age, I'm not that old and it wasn't that long ago, how much crap like that matters. I once spent a summer thinking about what I was going to wear to ninth grade. So, just move on. Don't give up. This road isn't easy and in the end, this is nothing. Even though right now it may feel horrific.