Hello Dear Thanks for your query For how many days are you having the problem?What is the stool volume and appearance ?What are the other symptoms associated ? Is there feeling of incomplete evacuation ?Is there blood in stool ? There might be many causes of this altered bowel habit starting from Irritable bowel syndrome to colonic carcinoma. Investigations should be performed for diagnosis : -Stool microscopy and culture (to exclude infectious conditions) -Blood tests: Full blood examination, Liver function tests, Erythrocyte sedimentation rate, serological testing for coeliac disease -Abdominal ultrasound (to exclude gallstones and other biliary tract diseases) -Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, malignancies) -Hydrogen breath testing (to exclude fructose and lactose malabsorption) Have a healthy high fibre diet.Take plenty of fluids. If you are having diarrhoea due to infective cause then you should have a course of Metronidazole.Irritable bowel syndrome may be a cause.In that case SSRI like fluoxetine will help you. But dont self medicate .Have a medical check up from a gastroenterologist and follow his advice. For gaining weight have healthy diet with enough protein [meat , fish , egg , pulses etc].Do regular exercises.Decrease the anxiety and have enough sleep. Hope this helps. Update here how you stay . Take care :)