have you considered he might be bulimic?
i'm not saying he definitely is. it's a possibility though.
-won't let you in his room because of binge food/bags of puke?
-covered his face up because of puffyness/redness/burst blood vessels from puking?
don't jump to conclusions, just keep a look out. and if he is, don't overreact, and do look up advice online - there are a LOT of misconceptions about eating disorders. listen to his side
are there any other signs? how does he act around food? does he eat very little at some times, then eat a lot at other times? does food go missing? have you noticed anything strange with his spending (i.e. does he run out of money quickly?)