1. It will all be ok. I know it doesn't seem like it but I promise, it will. You will be happy.
2. Your parents don't know what their doing. No parent does, but your parents especially don't know what their doing.
3. Stop wearing really baggy shirts. Stop it! It's not attractive at all.
4. I know you think you're fat and hideous, but
5. Purging is not good for you. You will fuck up your teeth and your metabolism irreparably.
6. You won't always be ashamed of your scars. Some day, you will bear them like a warrior.
7. Too much eyeliner.
8. Get help. Waiting until you're older isn't a good idea. Do whatever you have to even if it seems like it will inconvenience your parents. They're not the ones that are living with all your demons and they aren't the ones that will live with them years from now. There is no better time to get help. Once you fall in love and have a kid, going to rehab or a psych ward will not be an option any more.
9. Read less. Go outside. Learn how to be scared of nature and other people less.
10. Disobey your parents more. It won't matter as much in the long run and contrary to popular belief (also see number 2) they're not doing what's best for you. Also, your "rebellion" isn't bad, wanting to do the things you want is actually just a normal part of being a human being.