so it's really just to get it off your chest? Best case scenario for you he is in the closet, worst case scenario he flips a shit and never speaks to you again.
There is no way we can tell what his attitude will be once you tell him how you feel. For starters, is he aware that you're gay? If so, he probably won't be seriously shocked. But just maybe throw in there that you know he is straight and didn't expect him to reciprocate your feelings, but just wanted to tell him how you felt.
How are you in your final year of college and are 18? are you some kind of child genius?
Sometimes I worry about being a success in a mediocre world
-Lily Tomlin