Guys - I REALLY like this guy named Nate in my class.. He told me he felt the same way and he isn't?

This situation most commonly means that he pussied out.

He probally now feels things are awkward that its out in the open, so hes avoiding you to avoid the awkwardness.

Either that, or he told you he liked you as a joke to screw with you, and thats why hes avoiding you now. If this is the case, all i can say is move on, hes just like any other guy, a donkey! but if he truly likes you but hes just a bit shy and awkward, search him down at school, and talk to him. Make him feel comfurtable. Joke around with him. this will make him more open. Try asking if he would like to hangout that upcoming weekend. keep your get together a neutral setting, like the movies, or bowling. Something fun. then once hes comfurtable with you, you can ease into the romance. Please, dont be afraid to make the first move. you only live once. And in the end, the worst thing that could happen, is him say he donsèt want to hang out, which i highly doubt he would do. Good luck hun. Live for today. Yesterday is gone and over with, tommorow is a mystery. All you can control is TODAY.