I Have Been Taking Pantoprozole For About Four Years Now

I have been taking pantoprozole for about four years now and my refill required a authorization so I was out it for three weeks about five days ago I got it refilled and started taking it again and for the last four days I have had dirrea and greenstool and gut wrenching stomach pains I also have atrophic gastritis hiatial hernia gerd and turtuisity intestine .I also have had b-12 defientiency a lot will I have to take b-12 shots for the rest of my life because my stomach can not absorb any nutrients.