17 year old boy with a girlfriend/ex

me and mygirlfriend started going out she is 16 I am 17 we always talk on the phone everyday so thats kool and stuff..but because we live so far away its hard to see eachother but I mainly go up every weekend...she suddnly went cold on me so I ask her whats wrong and she said its not working...I being too kindhearted said the same but the problem is that we still love eachother but yet she said shes needs her space and wants a casual relationship....im really confused about things right now..have you got any advice please

this is really tricky, maybe try to see her more often then you r, tell her you love her and you want to be woth her