What Causes Stomach Soreness Inspite Of Taking Dexilant And Tums?

Thank you, My father is 88, he is complaining of constant stomach sour-ness . He wakes every day with a sour stomach, takes Dexilant, and Tums, or Gaviscon to no avail. He has recently had an upper GI series with no remarkable findings. His wife died May 12, and he lives alone with his dog. He was her caretaker for 5 years as she experienced Dementia. all he can talk about is his sour stomach. I have encouraged him to hydrate a great deal more. I have gotten him to stop drinking soda, most especially his longstanding addiction to Diet Pepsi with Aspartame. He quit smoking 35 yrs ago, does not drink, He is diabetic on oral medication, though he totally ignores his diet. What can I suggest to him.