Re: work injury
At this point, after you have been through several PT programs, etc. I think it is high time that you have a MRI or CT scan. You can only determine a couple things from a x-ray as they do not show soft tissue or nerves. If you had a bone out of place or a fracture, x-ray would be helpful, but you can't see what is going on with the discs, various soft tissue and nerves.
Are you being treated by a spine specialist? If not, I would suggest you make arrangements to see either a fellowship-trained orthopedic spine surgeon or a neurosurgeon who limit their practice to issues of the back and neck.
It sounds like your doctor thinks he knows what happened to your back, but since you haven't healed, it would appear that something else is going on, other than what you were "diagnosed" with. I have found that once a doctor makes a diagnosis, it can be difficult to get him/her to look further or differently. Sometimes it is necessary to go to a different doctor who is unaware of what the first doctor has done. Sometimes a different pair of eyes will see something the other has missed, or in this case, order a MRI which may reveal the source of your pain.