He could very well be depressed. I spent 3 years with someone like this that progressively got worse. He was taking advantage of me of course but was most definitely depressed also. He started drinking much more and by the end of the 3 years he was up to a pint of Jim Beam, a 12 pack, 2 cans of dip (chew), and had gained 100lbs. It was terrible and he was disgusting. I spent the last 6 months begging him to leave. Finally I had to call his parents to remove him from my home. I decided I didn't have time for him or his antics. I only wish I wouldn't have waisted so much time on him. I really hope this isn't the case with you. You should talk to him about how he feels and let him know that his behavior is not ok and is unacceptable. He should see someone and get help if he needs it. The entire family should not have to suffer. I hope it works out better for you than mine did.
It sure does sound as if he is severely depressed. Please get him to a doctor for help asap. God bless.
Sounds like either he has been smoking too much weed or he may be clinically depressed. See a physician to be sure.