Grrrr... Completely useless 'friend'

There is this guy I hang out with at college, a so called 'friend'. However, since day one he has been virtually taking advantage of me. He always comes to me asking for help with his homework. Me being myself, I never say 'no' and always agree to help him out. However, this is where the problem lies. Once I've finished helping him with his homework or whatever, he doesnt want to know me! He bitches about me behind my back, and is a complete and utter moron to me. Ive helped him time and time again, got him out of various messes, and its been virtually all taking and no giving. This is the reward I get for helping him, I'm vitually tossed aside and ignored once I've helped him. It has now come to the point that, I absolutely hate him, and still agree to help him. Im too shy to tell him to p**** off or stop using me. How do I get the message across to this moron I dont want to know him anymore? There's only so much a person can take. I've had enough.

Stop laying down on the floor and he'll stop walking all over you. You can't really complain if you are letting him use you. It's as much your fault as it is his.