Talk to Gastroenterologist on Unknown Diarrhea

Sir its been two years now that i am facing unknown diarrhea. It happens sometime due to milk and sometimes if i eat fruit alone.I am very much confused because one doctor in islamabad said that i have lactose intolerance and gave me medicine and His medicine which also includes lactase did not another doctor in multan which i discovered from marham said don’t eat fruits and ,i was concious about my ,i tried by about a week or two i was consuming 200 ml milk and was able to digest but not ,i came to know about day fresh lactose free first,i digested the after about two to three consumption i am again not digesting even the lactose free milk.I am very very also sometimes i digest ensure and sometimes i don’ help me.I want to gain height.I am an athlete.