You sound like me ... was it four years ago?? How time flies! I also had the clumsy feeling, twitching, cramping, percieved weakness ( maybe from so much self testing and muscle measuring) I would believe your doctor. Easier said than done though, been there... tried that....
Have you tried methylcobalamin B12? It was the cure for me. Although I still do have the odd twitch and other symptom, things are 90% gone thanks to my vitamin routine.
Take care.....Sandy