confused relationship need help

I have been taking to this girl now that I really like and she says she really likes me back. We have been talking for a year and 4 months now and don't talk to anyone else on the daily at all. However, every advance I make at making it an official BF and GF relationship she says she s not ready. Sometimes she says I'm her BF and then at times she makes it a point to say that I'm not. She says there is no one else but when someone never makes an effort to see you (she lives far) and she constantly rejects any advancement although she clearly says I'm not in the friend zone its just hard to tell what to do. I am 23 and have had 2 relationships in the past. She is 20 never had a bf but has had a lot of flings and hook ups. She says she is a virgin and we have not had sex over the past year and 4 months we have talked although we have made out. I have been nothing but patient, and loving towards her

But now when I ask her about us and becoming official she says i bring it up too much and gives me the silent treatment for awhile. Am I doing something wrong or what? what should i do?