How close was the time between your last B12 shot and the blood draw to test your B12? If you got your B12 shot a few days before your blood test that could give you high B12 results. I just had that happen to me. I was going in to have some bloods ran that my GI requested and there happened to be a B12 blood test in there from family doc that I didn't even know they were drawing. I get my results online and saw the B12 and it was high. My GI didn't even blink at it, as he said you could get high results from even taking the oral B12. I get my shots every other week also, and I too notice when I go longer than 2 weeks between shots. And its not a placebo effect either, it helps immensely. Sorry you are having such difficulties.
Last time my levels got near normal & I questioned the frequency of injections, my doctor said "well if you don't need it, you'll just pee it out anyway". That's a direct quote :)
Good luck on the new dr!