There is worst then my life, but I feel like talking about it anyways.

[Elektrisk]

Then my ex keeps flirting with me(btw, we are still best friends),

WHY would you put yourself through that? As long as you continue to talk/flirt with her, your feelings will linger. But, you can't have her anymore. You need to accept that. The only way to get over her will be to just go cold turkey. You need to tell her something like, "I'm still in love with you, and talking to you everyday doesn't help. I think we should stop talking." or whatever. Sugarcoat it how you will.. just get the point across.

she starts liking this fat emo kid

Don't dislike the guy. It's her choice whom she dates. It doesn't matter if he's fat, emo, skater, anorexic, or 65. It's up to her.

And all this crap is making my grades go down in school.

You are clearly depressed. I think you should talk to the school counselor. Nearly everyone school has one, and they are there for that reason. I know, a lot of people don't like going to the counselor for that reason, but swallow your pride and do it, 'cause you need to. You can't afford to throw away your basis for a good future over some girl.

Because when I am sleeping, nothing matters anymore.

And when you wake, those problems are still full blown in your face.