Your story is, unfortunately, all too typical of the experience so many of us have had with doctors. I got worse for 10 years while doctors said there was nothing I could do except take things like Vioxx and painkillers, wiping out my kidneys and liver.

I found a book that really helped, "Wheat Belly," by William Davis. I am convinced that most of us are suffering because of gluten in our diets. It's not just white flour; it's all wheat and barley. The glycemic index for whole wheat bread is higher than a tablespoon of table sugar!
The B-12 idea is a great one; here's why we need it so badly; gluten burns out the receptors in your gut that allow you to absorb B vitamins. After enough years of that, your nervous system has been starved into destruction. It takes about 6 months of living gluten-free to rebuild your gut, and possibly years to fully rebuild the nervous system. I'm on the journey now. It's not easy, but it sure beats deterioration while my doctors and Glaxo get richer on my misery.
You really can heal yourself. Good luck.