I cant stop thinking about this girl that don't even know that I exist and I tried most of what takes my mind off and I can help it!
Go show her that you exist.
Say "hello" to her.
well get to know her to see if you really like her
Communicate with her... Get to know her...
I had this same problem little over a year ago so I went to say hi to her had a nice conversation and here I am with her today... :) so just go talk to her say "hi" and go from there. Good luck:)