Am I being selfish or being used?

I have a friend who asks me to do things for him alot. Call the dentist to make appt, call for plane tickets, call and see if something is available at store the list goes on, anyway I want to help him out but I never seen to get a thank you and alot of the times he gets pissed because I I forgot to ask a question that the would have asked. When I tell him a thanks would be nice he says I am only doing things for him for something in return. Is a thanks asking too much? I find it hard to believe that everyone that does things for others strictly do it for just themselves, I like doing things for others but geez I feel used. If I am being selfish please tell me.