My hips hurt, I'm 14.?

Sometimes I use my stepper for an hour or for 30 minutes straight. But I never feel pain after using it. I only feel pain when I go out to places, and today my hip is sore from walking yesterday at the store. Yesterday I felt a sharp pain from my knee to my hip. Now that tells me something is really wrong. I want answers because I don't want hip replacement surgery, ouch. My mom thinks I might be walking with too much force or too fast. So, what's the right way to walk? And do you think the stepper could be a problem?