Welcome to NeuroTalk.

I think you should skip the doctors and injections...they are certainly not helping you properly.

Get your B12 level measured when you think the shot has worn off so you know what that level really is. Get the numbers and post here.
If in another country, post the nmol/L so I can convert them to US figures.

You CAN establish good blood levels easily with ORAL methylcobalamin, and taken every day on an empty stomach.
It WILL work even when you have no intrinsic factor.

Getting shots once a month with no testing to show if that is working for you is just sloppy, and makes assumptions that all people are alike.

There is a methylcobalamin injection, but they are compounded at compounding pharmacies and will cost more. I believe they have a short shelf life also, once made up.

Babies can be born to B12 deficient mothers, but do not do well and have neuro problems. I'd get the B12 test ASAP if I were you.

It is your decision to stick with doctors who are not treating you adequately, and take control yourself with oral. Many doctors do not believe that oral works...and they are wrong. Studies show it works. But you have to take a high dose like 5mg a day and only on an empty stomach for best results. Passive absorption takes place without intrinsic factor only in high doses.