What causes severe gnawing feeling in the stomach and chest after eating. Feels like bad hunger pangs. Not diabetic. Have GERD but take protonix (pantoprazole) daily?

Reflux likely. The pain location and quality indicate its origin is in the esophagus or stomach. It could be under-treated gastroesophageal reflux. However, at this point further testing might be indicated to ensure other diagnoses are not missed.