Am I being selfish because I hate sharing my stuff with him?
Why would you not want to be generous and sharing with him?
I find that's he's a total loser, and always in a bad spot in life.
Well, that's understandable. On the other hand, have you considered putting yourself in his shoes?
I'm tired of supporting this person. I'm going to give the money he owes me and never help him again. I've been trying to teach him lessons and help him out of the big hole, but he never learns.
You don't have to lend him money or anything else if you don't feel comfortable doing it.