ACL surgery january 16. can i start serious running now?

I had ACL surgery January 16 (hamstring graft). I am run cross country in college and I really want to start running. I havent yet and im at month 5. i get this pain behind my knee when i run i dont know if that is always there when you start or is it is not normal and its because i cant start running yet. I really want to start running again i need to be in shape for cross country. and i really want to start running for myself. i pretty much dont know how much running i can do?!!