Firstly where it hurts does not always mean that is where the problem is, the MRI will have been done looking at the very specific areas of the lumbar spinal cord and cauda equina that are giving rise to the various neurological signs and symptoms you have been found to have. MRI is pretty much the gold standard investigation for spinal cord issues and if there was an abnormality for example a disc protrusion this would have been seen. Sadly with back pain there is no easy fix.
I have severe back issues and MRI confirms 3 large disc protrusions and nerve root impingement along with an acquired scoliosis all due to osteo-arthritis. I also know at this stage there is not an operation that can fix it. This is directly attributable to my many years as a neuro-radiographer wearing heavy lead coats and lifting patients. I know only to well what back pain is like and I have good days and bad days ,I also function on opiate analgesia in varying doses.
The vast amount of back pain really is muscular and you say you have been pushing investigations yet you have had x-rays and MRI which are the investigations relevant to back pain. You have a connective tissue disorder which will contribute a great deal to your current discomfort.