Well, given you're already severally under weight...I doubt you would be able to survive more than a couple weeks without food. Probably not even that...you'll most likely be hospitalized way before that from complications. They can and will keep you against your will until you're stable and eating normally. When I was hospitalized for my eating disorder, there were some girls in there for months...and generally even after they left, they didn't go home but rather a residental setting. So...stop messing around and eat normally...or have all your rights taken away for a very long time.