Here's some info that might be of use--particularly eating cultured foods to help make use of what you are getting from your vitamin:
Vitamin B12 is vital for formation and growth of red blood cells. It is also important for the growth of your baby's nervous system; however, it is one of the most commonly deficient vitamins during pregnancy and lactation, especially among vegans. Vitamin B12 is found only in animal products but vegans can get vitamin B12 from fortified nutritional yeast like Red Star® Vegetarian Support Formula, nondairy milks, and cereals. You can also obtain vitamin B12 from supplements. Eating fermented or cultured foods (like yogurt, sauerkraut, miso, etc.) helps maximize the reproduction of vitamin B12 in the digestive tract.
Good sources of vitamin B12: Dairy products, eggs, fortified cereals, fortified nutritional yeast, fortified soy milk