Thanks everyone. I'll answer some questions that were posted.

No, he is not an engineer. He is in Social Work, with a minor in psychology.

Yes, he has some things on his mind, but nothing out of the ordinary besides his job and his school placement.

Yes, I have asked his best friend about his habits and moodiness and it seems this is something more. He seems unhappy most of the time, but when I ask him about it, he denies it. I internalize it, and think it's something that I've done.

To clarify, he is not just my roommate. He is my friend. I was not looking for a roommate. He wanted to get out of his apartment and suggested we live together. Since I am strapped for cash living on student loans, I agreed. He moved in in June of last year and he was a completely different person. We had people over to barbecque, we went grocery shopping together, cooked meals and ate together, and did social things. I went to his nephews wedding with him. I spent the day after Christmas with his family.

I have asked him if he likes living here and he says yes. I have suggested that we open honest communication and talk about how the living arrangement is going. He says everything is fine, yet he practically lives in his room. He comes out when I'm not at home. My expectations were reinforced by his behaviour over the summer and fall.

So, yes, that's why I thought that letter writing might get him to open up. He's had counselling before, and plans to be a social worker. He knows the methods and the lingo. Maybe he's afraid he'll hurt my feelings. Maybe he feels he's not pulling his weight. Maybe he thinks he's doing too much and I'm not doing enough. Maybe he feels like I don't want him here. So many maybes. I just want to know so I can either help him or move on.