J.P.
I would start at a chiropractor and see if they can help. If her back or hips are out it will cause pain in other areas of the body. Like any other doctors choose one carefully. They also work with orthopedics so if they think it is something they can not fix they will refer you to someone else.
I would be concerned about taking pain killers for such a long time even if they are over the counter. They are all made with different chemicals and can do other damage if taken over long periods of time.