Girl Problems?????????????????????

Ok so basically im anti social 21 years old and ive never had a girlfriend. This girl that i like used to talk to me when i would talk to her she usually smiled and me and had kind of a smirk on her face.....a good smirk. Whats weird is that i dont know but i got shy and kinda started to not talk to her. She dosent say anything or make any expressions when i walk by her anymore. Why? Also im involved in a certian activity with her all the time. In college this activity is 4 days out of the week and many practice hours on the weekends. How could i start to commmunicate with her. She dates some pretty popular guys, and i think she may be a little out of my league. But i feel like she used to really like me because im talented. What do i do and why is this happening?