this sounds like what i went through this last winter. i am sorry, because i know that you won't want to do this, but this is what i did: i told one of my friends who had already been suspcious that i was in an eating disorder about it. so she practically made me eat and made sure that i wouldn't purge or use laxitives (another thing that i was doing). i couldn't have gotten through it without her, but unfortunately she alone couldn't help me. i eventually needed to go to a doctor.

i think that your first step is to tell your best friend or someone you really trust. they can definately help you through it.