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
-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 :)