This is most likely to be due to Acid Peptic Disease or acidity as is commonly called. Pan-D is to be taken on empty stomach and you should not eat anything afterwards for at least half an hour. You should eat slowly. Eat healthy. Rather than one big meal, eat smaller portions at frequent intervals. Keep regular schedule for eating. Avoid coffee and tea. Life style changes also help (including regular exercise, adequate sleep at night). If your problem persists, you should go back to your doctor. I hope this answers your question.