OK, from a woman's prospective:
Yes, girls are crazy at your age, so are guys. Very few people know who they really are at 18. It's called gaining life experience and growing up. Believe it or not, this break-up is a good thing for you right now.
Don't go man whoring around. There was a period in a friend's life that he would sleep with any girl that smiled at him. Then he met his wife. He wanted to be serious with her but she blew him off (why would she be any different from other girls?) Every chick in town (and a few surrounding ones!) thought of him as just a "good time" for a night. Took him a year to prove to her he was serious and not just looking for a lay. Slutting around, man or woman, comes back to bite you in the ass eventually.