Is this girl playing with me,please answer.. :/?

ive known this girl for a while now, and we have become really good friends, but in the past she has known that i have liked her.. but then rather us stay mates.. so we are still friends but she keeps being really friendly and then getting my hopes up to wonder if moving direction into a relationship, but then.. she will back off and be really plain and dull with me, and its becoming a repetitive circle of the same routine :/ i really like this girl but its starting to hurt more and more each time. i cant stop thinking about her..