Numbness and Tingling, something other than B12?

I have had numbness and tingling everyday for the last 9 months. Sometimes it is a foot or hand. Other times, it is both feet, both hands and my face. The only thing the doctor has found is a slight B12 deficiency. I have had bi-weekly B12 injections for 5 months. At first, they really helped and gave me a few days of relief between each shot. But, they do not help any longer. I am feeling numbness somewhere all day, everyday, even with the shot. I think my PCP and neurologist are stumped.