I "love" this girl but she has rejected me... twice now...?

[Thisguy]

Sorry for posting this again and again but I seriously want help.

Short version: Girl rejected me twice. I still kind of like her. I try to avoid her. She still makes many attempts to talk to me. I don't know what to do.

Long Version:
I am VERY sorry for this much writing.
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 about 5 months later, I basically told her that I'd like a second chance and she turned me down again (she said that she wasn't looking for a relationship but I think that was just her trying to make me feel better). 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 wanna like her... And the last 2 times I've seen her over the weekend, she's texted me like twice telling me that I should come sit and talk with her and our other friends. But I usually just make up some excuse and don't go over with them.
Us and our other friends have a 6 person group chat on Facebook where I talk to her a lot. And we text each other every now and again. Even just yesterday she texted me because I was Facebook messaging one of friends and she was hanging out with her so she texted me kind of relating to the conversation that I was talking about with her friend. And this is not in the day time, this is like past 1 AM. I didn't respond to the text though because I wanted to see what would her reaction be if I did not respond to her. It's usually her starting our text conversations, though.
I'm not sure if I should continue to avoid her anymore or what, though. I think about her every single damn day and it bothers me. I am actually kind of afraid that I am obsessed with her, but i don't stalk her or anything. Like I said, in fact, I try to avoid her... I am sorry for the long message but can someone give me their opinion on this?! What do I do now!?
I also feel like I am being very selfish and self-centered because I am avoiding her when clearly she wants to talk to me...