Does your college have a counseling center? I got help at mine. They're geared to the stresses at college.

I use to play with rubber bands, things that were "quiet" when I was anxious (shredding napkins or tissues? :-) Can you do some sport/activity that will wear you out a little bit? I read one place about how, if you grind your teeth (at night/sleeping) that that is similar to your brain twiddling its thumbs :-) and if you eat a bagel or apple, it will "wear out" your jaw muscles so you won't do that behavior. Maybe you can figure out something to do before classes that are hard so your body can relax more?