I seriously hope this isn't a shens -_-
At any rate, don't listen to half of these morons. Most of the people here feel all high and mighty behind the computer, but few would actually do as they say.
I'm in College rooming with someone as well whom I don't see eye to eye with a lot of the time, so I have at least a small inkling of what you are going through. If it were me in that situation:
1. Don't get pissed off and start yelling like half the people here believe you should. That is only going to make matters worse. Seeing as he is apparently bigger than you, that = bad for you.
2. Explain to him calmly that this isn't fair to you for a number of reasons.
3. You are men, don't start telling each other how you feel about things, just be straight forward with him.
4. If he refuses you have to bring in your landlord or the police into it. You pay rent, you haven't done anything wrong, he has no right to kick you out. Especially if he is using your bed and your possessions (Sheets) for whatever he feels he wants.
In short, don't let him walk all over you- be firm. However don't act like a stuck-up jerk with a chip on his shoulder.
Good Luck, I hope something works out for the better!
-Kevin