There are many of causes other than heartburn or H Pylori gastritis. This can include functional dyspepsia (non-ulcer
dyspepsia), peptic ulcer
disease, GERD, gastric or esophageal ulcer, biliary tract disease, gastroparesis, pancreatitis, malabsorption, medications (i.e. NSAIDs, potassium supplements, digitalis, oral antibiotics), or metabolic disturbances to name a few.
It seems you have undergone empiric antisecretory therapy (protonix) and H Pylori testing.