S.M.
Take him back to a doctor, maybe not the same doctor, but he can weaken and die from dehydration and malnutrition if the diarrhea isn't brought under contgrol. It's not just a bug if it lasts this long. Please get help. He may be allergic to something he ate, or he may be reacting to some medicine the doctor prescribed. He needs help, quickly. I would go to the Emergency Room, especially since there is blood in the stool, even though it may be just from his anus since he's irritated. None of this is a good sign.