Suggest Treatment For Blocked Heart Valve

I had a stroke in 97. a rare Type of Pneumonia in 2003, Lost my hearing in both ears, only came back in one. I had open heart surgery in 2012 with 3 valve replacements, one being the main aorata. Now the doc says that one is getting blockages and he said I need to take b12. Didn t do any blood work. Can you get too much b12. I stay tired all the time, stagger around, almost falling and dizzy. I will be 80 in OCT.