What could be the cause of my severe b12 anemia?

Background: 19F, 150lbs 5’5 I have Hidradenitis suppurativa, and Ehlers danlos, and I’m not sure if this is important but I had long Covid for a long time. I take birth control and cosentyx.

About 2 years ago I was diagnosed with a b12 deficiency because I was having trouble staying awake and I was suffering from severe headaches. I was put on b12 supplements but they didn’t help much so I switched to the injection which was every 3 months. This past year/year and a half I suddenly have started to have symptoms much quicker now which had made me need the b12 injections every month. I get extremely tired, fatigued, unmotivated, and I have tingling in my fingers and severe headaches and when I need my injections it’s almost instant, one day I can be okay and the next I’m down for the count. None of my doctors have told me why this happens though, nobody in my family suffers from this, I have a normal diet, I eat plenty of meat (obviously not too much) I’m not vegan or on any special diet, and yet it’s getting worse. What could be happening to me???