For the past 3 days, my son has been vomiting every time he complains of a stomach ache. He doesn't have a fever and it only happens once or twice a day. When he vomits, it's just mostly water with a little bit of white mucus and it's only a little bit of vomit. After he vomits, then he's fine, he goes and play, but this is happening for a couple of days now.