Hi. Thanks for your query. Noted the history black watery stools for 2 years and undergone colonoscopy for the same. They found nothing, There is pain in abdomen similar to having miscarriage. Upon increasing fiber and water the stools are not watery but still soft and sometimes black. I would advise you the following in such a situation: Send the stool sample for lab tests on three consecutive says. Tests of blood and urine and ultrasonography to start with to get a proper additional information. CT scan of the abdomen. All these investigations will lead to a proper diagnosis and a plan for management.