Talk to Gastroenterologist on Undiagnosed

hey very concerning point . From past 6 months my digestive system is a mess I get diarrhea in an instant I went to a gastroenterologist and he suggested a CBC ,celiac test,stool test and urine test and serum crp and esr test and all test came back normal . he gave me a librax and delanzo said when u feel diarrhea eat these 2 other wise everything good . but still u can't eat spicy food and eggs and can't drink milk plus eat vegetables like Brinjal ,cauliflower even if I eat salad lettuce tomatoes I get severe black poop and normally I get very watery diarrhea if I drink milk or eat any dairy based product and my diarrhea stops once I take banana jucie or have fennel seed tea . Can any doc help me with what the hell is wrong please