My 14 year old son has had mild diarrhea ever since we got back form South Africa this was about a month and a half ago first I thought it was a virus picked up at school and tested him with milk ferments it got slightly better but he still carried on with mild diarrhea since then I have taken him to see a doctor who felt his abdomen and advised me to have his stools examined the result was negative he says he occasionally feels as if he wants to vomit he is getting hot cold flashes and diarrhea has increased could you advise me what to do? Thank you