I'm a college student myself, and all I can say is that you need to watch the drinking. Really watch it. I keep detailed records of all the food/drink I intake, and a night of heavy drinking will add an extra 2000 calories and you won't even really notice until there's a big spare tire hanging off your gut. I kept it off my first year by not drinking at all, but my second and third years weren't too kind to me. I've always ate very well, but I'm just now regulating my alcohol intake and getting into the shape I ought to be in. If you need to be drinking, either find someone that's 21 and stick to the straight liquor or mix stuff with Diet Coke, or get yourself an ID and drink Long Island Ice Teas, cause those are pretty much all spirit.
On a further note, when everyone else goes and orders pizza or whatever other terribel greasy food they get . . . don't eat, or find yourself some tuna. Your body can't handle carbs late in the day/evening.
Lastly, if somehow you're not in a dorm and on a meal plan, find a Costco or Sam's Club, and stock up on chicken and stick with eating that. Making it through college without getting fat is all about willpower unless you're one of those genetically gifted types. Try not to let the hangovers get in the way of your workouts, cause it's way too easy to get off track.
If you're good, you'll listen, but it's hard. So good luck.