As difficult as being hungry all the time is, if it happens when you get B12, it probably is a sign of your body attempting to repair.
If you are low in B12 after all that, you store horribly. Or, if the shots were not methylcobalamin, you might have a rare inability to convert the other type to a usable form.
Are the shots definitely the methylcobalamin type?
I will be adding much more to my B12 website, but it can help you with the basics already. Check it out.