Would this be an eating disorder?

I don't know what it is, Alex, but you need to speak with your parents who should take you to a doctor. Especially given what you have put in your post in the depression forum. Print your posts out and show them - showing someone something written is often a lot easier than having to tell someone verbally.

Alex051 wrote: OK well like sometimes i go without eating for days at a time. ive never forced myself to puke (although i try) even tho i only way 70 pounds (im 13) i feel fat. is this an eating disorder? or just low self esteem.

I have the feeling you know this is the definition of anorexia. Yes?
Low self esteem drives anorexic behavior. I'm no expert, though. Joobles has very good advice- you should follow it.
Good luck! Let us know how it goes!