Welcome to Just Answer.
I think you may have a condition called spinal stenosis which is when the spinal canal bvecomes narrowed squashing the nerves which control movement and sensation in the body.
An MRI would be a good idea but I would advise you to see a neurologist who deals with this type of thing all the time and get whichever tests he feels you need, done through him.
I do hope this helps and I hope you get this sorted out very soon so that you can get back to being painnfree.
With my very best wishes