The persistent nature of your symptoms warrants a medical evaluation. Any number of conditions could be causing your gastrointestinal complaints, and some could be serious. Dietary intolerances (lactose
, etc.), collagenous colitis
, inflammatory bowel disease
(e.g., crohn's disease
), bacterial overgrowth, and irritable bowel syndrome
could all be at the root of your symptoms.
If you haven't seen your physician yet, i urge you to do so. I've attached some links that might be of interest to you.