If so many Doctors in Private and Government Hospitals could not diagnose your problem in spite of  seeing you and examining you , don't you think it is too far fetched to expect a diagnosis from a Doctor who has never seen you ? This point is significant because you are only 21 years old and you have been going to various hospitals for the last 3-4 years.

Avoiding spicy foods and junk foods and using antacids can help… for for proper diagnosis for your problem in passing stools requires more information and history

Using antacids may help ease indigestion. Eating smaller meals more often, chewing food thoroughly, losing weight and avoiding triggers such as fatty foods and carbonated drinks may also help.

Ok the basis of your history and symptom that your have indicate an that it's can be Gastritis or IBS ( irritable bowel syndrome). So in this condition you should follow good life style like drinking sufficient amount of water and do exercise regularly with yoga and meditation. Take less spicy and fatty food.