Hi,
As per your history and symptoms most likely you are suffering from 
irritable bowel syndrome. Irritable bowel syndrome is a rather common intestinal tract disease which is characterized by stomach gas, diarrhea or 
constipation for months. It is a chronic condition whose exact cause, although unknown, is sometimes attributed to the dysfunctional production of the 
neurotransmitter, dopamine. Initially, I would suggest you go for stool microscopy test. If the test is negative for bacteria or protozoa (
gastroenteritis chronic) then it is irritable bowel disease.
Suggestions are:
Start taking a probiotic, Probiotics contains 
lactobacillus. These are good bacteria's help in proper digestion of food and will help to revive your depleted gastric flora. Gut flora is the complex community of microorganisms that live in the digestive tracts of humans.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. Ivan R. Rommstein, General Surgeon