Hi My Major Area Of Skin Become Senseless. At Left

Hi
My major area of skin become senseless. At left chick, forehead, left leg and in private part also. My vitamin B12 count was 130, I completed course of 20 injections and tablets which need to put under tongue. But still senseless is there also penis in not getting full tight as was in previous years. I am 39 years old male, please guide me about route cause, treatment and to whom should I consult.