A side effect of benzo withdrawal is muscle spasms or muscle pains. I had back pain getting off Ativan. First, lower back spasms. Then a shoulder injury, neck spasms, jaw, head pain, etc. Four of the six times I went to the ER were for body pain from the benzo, so I can imagine what you must be going through. It will pass over time. The challenge is getting through it. I would bet money your doctors find no explanation for the pain on tests or scans. I have read story after story where this is the case.
The catch-22 is taking other meds while you are in withdrawal. Be aware that polypharmacy (more meds) can complicate and/or further harm a person. There is no such thing as a risk-free pharmaceutical, especially when your CNS is sensitive from the benzo withdrawal; you don't know how your body could react. You are lucky the pain meds have worked. For some folks, they do not work at all due to the effect the benzo has had on their system.