Boyfriend and girlfriend is a fragile time. There's no commitment, and if you are too young (16-25) it's easy to get bored and move on. Depending on the girl you've attracted, she will come with a level of maintenance. She might need more space, more money, more time, more logic, more emotion, more masculinity, more femininity, more God, no God, more penis, more vagina, more purpose, more freedom... Everyone is different.
You sound a bit like me. You want to grab a hold of her and not let her go because they all slip through your hands. Your daily interaction makes you high maintenance too. I think your best bet would be to go on more dates. Only contact her when there's something important going on. The romantic "ILY" just doesn't fly with most types of women these days. Lastly, I think you should be prepared for another break; not that you did anything wrong, but it sounds like she's already made other people a higher priority than you.