If you don't have any luck with your physician, consider seeing a Naturopathic physician. They are well known for giving B12 injections. You can also purchase B12 drops (do not get the tablets though) at Walgreens (Nature's Bounty is the brand, I believe).
Good luck !
You can go to your physician and ask for them. I have nutritional issues and so my doctor gives me a prescription for the B-12 and the syringes and I give myself the shots at home every 2 weeks. Good luck.