It appears that you have now had a fusion of L3-S1 (the lowest three levels in the lower back) and you have continuing pain. The differential includes failure of fusion at one or more levels (pseudoarthrosis), malalignment of fusion, continued compression of the neural elements, chronic radiculopathy, arachnoiditis or sacroiliac syndrome.
The work-up includes a new MRI, a CT scan, a thorough evaluation and possibly some diagnostic blocks. Treatment may include further medications, therapy, surgery or neurostimulation.
You would need a close evaluation by an experienced spine surgeon.
Dr. Corenman