What Causes Pain In Hip And Leg?

My name is mason, and I'm almost 20 years old I'm a 2nd year college student; studying business and accounting. I recently started having pain in my hip and it's moving to my leg. Almost 9 hours a day its hard for me to walk, but my doctor tells me he dont want to put me on pain medicine right now because im too you, but he will never tell me whats wrong. So my question is what could most likely be causing the pain in my hip and leg?