I have had lower back porblems for about 6 years and have had mutible injections, including ephidurals. The week after xmas I went in and had L4-L5 and S1 or 2 nerves buned off.. I still have pain in my lower back and sometimes my feet now feel really cold. I cannot do any lifting more then 15 mins. or I will be paying for it...
I need to know your walking distance. It might be severe lumbar canal stenosis. If basic interventional procedures do not help try to consult a neurosurgeon or change your pain physician for get knowledge about advanced pain procedures. You have options like nucleoplasm, angioplasty, HY Chat Doctor.  I need to examine you and see your scans for giving you exact diagnosis.