Taken Guy Trouble?!?!?

Okay, so just to give you a little info, I'm 14. Just got out of the 8th grade. so i've recently moved into this small town. The first day of school I noticed this really cute, outgoing guy. Within a week, he asked me "hey, do you have a phone?" on Facebook. And of course I gave him my number. But here's the catch: He has a girlfriend. They have been going out for over a year. (we are in the 8th grade... how serious could this be?) They have NO classes together this year and me and him have half of our classes together. But he treats me like his bestfriend and a mixture of girlfriend. We always text and be flirty. And we go to the same church. (He invited me) We are always by each other. And i always kinda stick by the 8th grade guys because i'm the only 8th grade girl on Wednesday Night. So we are always flirty and mess with each other. And on Sunday Mornings in Sunday School we are in the same class. He always saves me the seat by him on the futon thing. And we always joke around. I like this guy soooooo much. The only problem is the girlfriend.... what do i do??