Hey, I'd like to say that, if you ever need someone to rant to, to get advice from or just to be friends with, you can PM me. I'm usually online. I'm also sorry that you feel as if you have no purpose, because everyone does. It could be to make someone else happy, to help someone to understand something, to help others in tough times or just being here for someone.
Look, I don't know you personally. But I want to at least try to help you feel better about yourself.
If you don't want to take up my offer, it's fine by me. Just get someone to help, so that you're not alone in this "battle".
Hope you feel better soon!