I'm not a doctor but here's my two cents. You really should see a doctor and get a definitive diagnosis on the gluten intolerance.
As for the problems with the B12 --- did you look at the ingredients label to see what else is in it? Quite possibly, you could be allergic to one of the inactive ingredients. Or you may have a problem with B12 in general.
If you truly have a B12 deficiency, then you should discuss with your doctor about the possibility of getting a monthly injection of it.