Your pain seems to be focused in your lower back with some radiation to the legs. Your MRI notes degenerative disc disease at L5-S1 with a bulge at that level. You do not describle the severity of the bulge nor the quality of the degeneration of the disc at L5-S1.
Your pain could very likely originate from this degenerative level. With years of symptoms now confining you to bed, you would do well to obtain a workup by a spine surgeon. This might include discograms and even selective nerve root blocks (see website for explanation of these). You might be a candidate for a fusion.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.