Suggest Treatment For Stomach Pain And Vomiting In Infant

I have a 3 year old, he has been complaining of stomach hurting for almost a week. Today he got up and only drank water, like an hour later he started vomiting numerous times that looked like cottage cheese and now this afternoon, he is vomiting up foam, should i be alarmed. He is on his way to the emergency room but I am worried it could be something serious