My 18 month old has whooping cough we are on day 11 since it started and he's really no better but I'd say worse. Full of mucus now. But he's finished his course of anti buotics to stop him being contagious but he hasn't pooped for 4 days as when he try's to eat the cough starts and he vomits. However he's still drinking a lot of having wet nappies. At what point does the no pooping become a problem?