I searched the net, and found someone with this who said it was due to a severe vitamin D deficiency. Vitamin D deficiency is linked to insulin resistance. Do you get plenty of sunlight, or take vitamin D supplements?

On another website.

"Other considerations would be GERD, ulcers, gastroparesis, pancreatic or gall bladder disease. Test to evaluate these disorders would be an upper GI series/upper endoscopy, abdominal ultrasound or tests for the pancreas, including pancreatic enzymes."

It might be hypogycemia, in which case a low carb diet, and 5 or 6 small meals spread out per day and no large meals might help.