Amazing how many, especially woman, have the same issues then yours, after several years with constipation, diarrhea, etc. and doctors telling me I have IBS live with it I finally was diagnosed with collagenous colitis after a biopsy during a colonoscopy, the only way to diagnose this disease, can not be cured but kind of managed with medication and diet. I am also gluten sensitive, lactose etc. at least now I know the cause of my colon issues and can handle it better. You might especially at your age have this checked better then the not knowing.