You might have pernicious anemia--meaning your immune system has DESTROYED your stomach's ability to produce gastrin--but you might have gone undiagnosed as doctors check B-12 levels AN INVALID TEST FOR ANYTHING! Get a blood test for gastrin levels (You don't even have to fast.) and intrinsic factor antibodies (You must fast.)

But you could just have S.I.B.O. or diarrhea-dominate or CONSTIPATION-DOMINATE bacterial overgrowth. A company in Boston does a quite valid test for about $300 that you can do by mail. For get your own health history (except what your instincts tell you because "modern" medicine is pretending you can only have what they PROFIT from treating. But you must get informed. It's a long process, but start with SUPER GUT and the writings of Dr. Gundry and anything you can find on S.I.B.O. But most of all, you MUST follow a SIBO DIET, which means don't be feeding the bad bacteria by eating refined carbs or sugar! (The book SUPER GUT explains that we Americans have gut entirely different, for example, that the guts of people in the Australian outback, WHO DO NOT HAVE OUR ILLNESSES!) You need probiotics but you need to read WHICH ONES and understand that things like grocery store yogurt is useless.