The girl I "love" rejected me twice... Help...?

[Thisguy]

So I am a 17 year old boy and this wonderful girl entered my life and she was considering dating me but she rejected me and then my feelings never subsided and then (about 5 months later) I basically told her that I'd like a second chance and she turned me down again saying that she was not looking for a relationship right now (but she said that to make me feel better, right) and even now probably a month after that, I find myself unable to not think about her constantly.
I've started to completely avoid her in person though. we have a school activity where we see each other on every few weekends. But I avoid her cuz I don't wanna like her... But I do... Us and a few other people have a 6 person group chat on Facebook where I talk to her a lot. And we text each other every now and again. It's usually her starting the conversations, though. I want her out of my head but I also don't want her out of my head at the same time. I'm not sure if I should continue to avoid her or what, though