What is this oily patch in my hair that wont go away?!?

Ive had it for 3 months. Im a 23 year old female and have been on birth control for 7 years.I have this waxy oily patch in my hair. I went to a beauty salon and this lady said to use clarrifying shampoo once a month because anymore than that is bad for my hair. I did use it and it worked great, oil gone BUT it came back the following week. Could this be a hormone imbalance caused by my pills? If so, what would it be? THanks!