How do you know if it's past just a simple crush?

Okay, I've liked this one girl for probably nearly a year now, I liked her for a few months and then suddenly went off her, then after I got to know her a bit more I suddenly started to like her again more than I did before. Now it's just progressed more and more and I can't help but think about her. Sometimes I think to myself it's time to try and move on but then the moment I start speaking to her I suddenly become mively infatuated again. I dunno what to call it, love? Because I don't think I've ever been in love, although this seems more than just a crush.