Finding out someone doesn't feel the same way about you feels like the end of the world. You put yourself out there, only to get knocked on your back. It's not easy to have feelings for someone, and honestly, rejection is a bitch. Luckily, the patron saint of unrequited love is here to give you the best advice I can.
First of all, don't feel stupid. If I had a nickel for every time I liked a guy who didn't like me back, I would have the world's largest collection of nickels, and I know I'm not the only one. Liking someone who doesn't reciprocate those feelings is the story of almost everyone's life. Don't feel like an idiot because you liked someone, and they didn't like you back. It happens to everyone. If it didn't, polygamy would be much more widely practiced in the world.
Second, this doesn't mean you are any less of a person. You are not defined by who likes you. Harry doesn't want to date you, but that's because he's probably stupid and not because you are not beautiful, smart, or funny. It has nothing to do with you. It is not your job to make people like you, nor is it possible to force it if it isn't there. You wouldn't want to be with someone who doesn't like you. There are enough people in this world who do like you and will like you for you to define your self worth by one stupid kid who doesn't realize how much you are really worth.
Take some time for yourself. I know it's often said that "the best way to get over someone is to get under someone else," but public service announcement: that is bad advice. Run yourself a nice bath, put on a good rom-com, and take a couple days or weeks to heal. Even if you did try to get over this with someone else, the feelings from this heartache will still be there when the other fling is over. Deal with your emotions, don't try to cover them up with a new person to like.
Lean on your friends. A GNO is probably exactly what you need to take your mind off of all the crappy effects boys can have on your heart, even if it's just a trip to Olive Garden and impulse shopping at TJ Maxx. Lose yourself in endless breadsticks, and buy two cute pairs of socks you don't need. You deserve to treat yo' self.