My son is 9 and has been ill since Saturday. A day of vomiting-3 or 4 times. Then diarrhea started Sunday I think. He's been off his food, until the last 2 days, yesterday ate the most but still not loads. The diarrhea has increased today, much more frequent. He has been drinking plenty of fluids-just water. Is there anything I can or should do? Someone suggested imodium but chemist assistant advised to just let it run its course. When do I need to call the doctor? Tia.