That sucks.
Seriously, I'm not going to try to make all the stuff that's happened to you sound better because I hate when people do that. I'm so, so sorry you had to go through all that crap.
On a happier note, I hope this forum will be really good for you. It's not embarrassing to spill here because nobody knows you personally but everyone knows what you're going through, or at least has an idea where you're coming from. Just keep posting and read through other stuff on the site - there's a lot of support out there.
Someone once told me about categorizing your life into things you can't control and things you can. The things you can't control (past abuse, for ex) you can't dwell on because there's nothing you can do to make them better. Put your energy into the things you can control - your GPA, your relationship with food, etc. There's absolutely nothing stopping you from making the changes you want - no one's planned out the rest of your life for you, you can shape your life and habits into whatever you want. Yeah, it's hard, but so is everything worth fighting for.
Start slow - don't deprive yourself, eat around every three hours, and make sure you're getting enough calories so you won't be as tempted to binge. Don't outlaw certain foods because you'll end up wanting them more; have a little and move on (it's tricky to do that, but not impossible). Don't make yourself feel guilty if you're not perfect - a lot of binges stem from guilt over doing some "unhealthy" thing that actually wouldn't be so bad by itself! Try to exercise, but don't be so rigid about it that when you don't you feel like you've failed and then binge again. If worst comes to worst and you can't stop yourself from bingeing, try not to purge afterward. It's not the end of the world, you'll do better next time. Most importantly, please, please don't be too hard on yourself. I can't imagine how difficult it is to feel like your life is crashing around you like that, but don't lose your self respect. There is NOTHING wrong with you, you can be a pediatrician or a neurosurgeon or rocket scientist or whatever the hell you want (I actually think your experience with food issues is valuable in a nutrition-related career, because you can understand other perspectives on food and health).
Sorry about the novel (I got a little carried away), but I hope it makes you feel at least a little better. Keep posting and check in with us all the time, it really helps. We'll help you beat this thing, but don't beat yourself up too much along the way, okay? 
...have another smiley face, you deserve it... 
... and another ... 
... all right, that's quite enough.
P.S. I'm 17 as well ... these teenage years are always so freakin fantastic, huh? (Ha. ha. ha.)
