I don't use drugs, and I don't feel as though I have a hard time making friends. I am not, I don't think, homesick. I am however, somehow uncomfortable with college stresses. I don't feel crazy or insane, just a bit uncomfortable. You are probably now living with a roommate, certainly someone you did not have to share your space with last year.
Light also affects one's mood.
It hasn't been particularly sunny out, and being indoors under artificial light, people tend to feel tired and depressed. Give yourself some time to adjust.