What Causes Appetite Loss In A Child Suffering From Fever And Stomach Ache?

My son got sick last Sunday morning. high fever severe stomach pain. he pulled his knees to his chest for 3 days and I took him to doctors on Tuesday and they evaluated him for appendix. at the time the dr said he didn t show signs of that pain of appendix but we should evaluate him for a couple days since fever was gone. So my child still has not eaten since Saturday and fever never came back but he still from time from time complains belly hurts and will not eat and threw up again today. But other than that he does nothing but lay on couch doesn t want to play. he is 5 years old. He says now his belly does not hurt but he has now thrown up like every three days and just wont eat. I called doctor and they said they think I should take him to ER but he doesn t act that much in pain. What do we do?