Dude, I've been there. A lot of us have.
I was about your age when I had my girl trouble. I met a girl during the end of my freshman year. The first time we met, we ended up talking for 8 hours. It was amazing, I'd never met anyone like her. We start dating and things are wonderful, and stayed wonderful for about 3.5 years (we were talking about marriage, etc). I'm looking at rings, I told my parents I was thinking of proposing, etc.
Then on a random Friday night we're talking about graduating and future plans. During this discussion, she tells me she doesn't think my plan would be wise "financially". I explain that I can manage money, and it will be fine if I'm/we're responsible. She says ok, and acts like things are fine. On the next Monday, she comes over to my apartment and breaks up in the most soul-less, emotionless way possible. She said she didn't think she could have a future with someone who's 'financial goals' were so low (basically I wasn't going to make enough money). To make things even better, she begins dating one of my best friends a month later. He didn't even have the stones to tell me. My friend and I never spoke again. Between 'losing' her and a friend that was like a brother, I was DESTROYED. I only left the apartment for school or work for about 3 months, then moped around for about a year. For the love of God, I listened to emo. EMO!
I look at it now as the biggest waste of time in my life. I couldn't see how lucky I was to dodge the bullet I did. I let her take a year of my life, and I still kick myself for it.
You've been told this a dozen times, but there are plenty more out there....some of which are actually a tolerable level of crazy. Go on, live your life. Trust me, living well is the best revenge.
