I Am A Veteran With A Questionable Health History Since

I am a veteran with a questionable health history since 1988 while in service. I am wondering if ailments such as gastritis, gastroenteritis, 5 events of gastroenteritis, and Gerd, and I have been treated for IBS, esophagitis, and pharyngitis as well; are related to the anemic conditions I am being treated for now. I was told I was mildly anemic prior to leaving the service and two years after I left the service the VA began treating me with monthly B12 injections and daily Iron tablets. I am told my anemia is not a result of any of the ailments listed in the beginning of my question. I would like to know what the relationship is between the ailements and anemias and how to connect the dots to diagnose the anemias root cause.