If you could write a note to your younger self, what would you say in only three words?
I had two thoughts. 1) Words can hurt. 2) Try your best.
What would your note say? 
Or what I always said to myself when I was younger, I'd say to her again to reaffirm it:
You got this.
Live for today
Don't be lazy
You need help.
Not just from doctors or to be poked and prodded in your mind, but by friends, and family. Let them in, maybe not all, but a few trusted people who can help. It's not a burden, you need this, and they understand. You need to be helped by people who care about you in way you don't care about yourself.
Remember to breathe
Trust no one. Don't try to be anyone you aren't because it will literally almost kill you. You're different for a reason, don't be ashamed of yourself. Go get help while you can. You need it even though you say you don't
Please, Just Cry.
Don't do it.
Keep on moving 
Eat less and be fit