Welcome to Neurotalk:

First thing I think you should find out is what your current B12 test reading is. It could still be low, because doctors don't understand the lab ranges in US are outdated.

If you are below 400 and having chronic symptoms it might be because you need more B12 to get into a good reading range. If you get shots, you should wait at least 72 hrs to a week before having a blood test.
Otherwise the result will reflect the shot, which leaves the blood in 72 hrs. That would give a false high reading which would be low the rest of the time until the next injection.

So see what your last test was. Get the numbers etc. How do you manage the pernicious anemia? What dose and how often?

Also you should get the Vit D testing too. Many people who come to these boards with chronic illness and pain have very low Vit D. Fixing that often helps alot of your daily comfort.