I have had back pain ever since I realized something was not right with me: 6-9 months before I was "officially" diagnosed with PD. Exercise, such as BIG Therapy, Yoga, and swimming, has helped. Walking has not helped, it actually heightens the pain (at least for me). I have not discovered any meds, including over the counter meds, that can help. Besides asking the doc, I would seek assistance from a PT.
For whatever its worth...