Dont feel terrible, im sure he will be home soon.
I hope you can get a solution at the doctors. Its hard with teens as with my dd i always put it down to her being lazy, the not getting out of bed, doing homeword even doing menial things but my dd has a good friend who has just be diagnosed with depression lately and her parents mentioned alot of different behaviour to my dd. I think My dd has self esteem issues not depression. They are certainly a bread that is easily misunderstood.
Hugs and i hope he is home soon