What Should I Do About Loose Motions In My Toddler With Stomach Pain After Food And Dark-colored Stool?

Hi, my 3yrs son having loose motion last 5-6 days, initially given metrogyl suspension for 5days, but after 3days agin the frequently motion happens so started antibiotic mox redimix suspension, and sporlac power. But i stop sporlac power user after one day bcz motion was 5times in a day.But i have given ORS in water. Now antibiotic will end tomorrow still after eating food stomach pain happened and after that moton also. Food is also given mostly boiled potato and boiled raw banana. Today motion color is more to black at the morning time but after that not black but not much mucus. Please suggest what will do next