What Could Cause Stomach Pain In A 9 Years Old Child?

My 9 year old son has been for over 10 days. He is complaining of stomach pains right by the belly button. I notice that his feet are so cold, which this has never been. I have taken him to his pedetrician also 2 emergency visits to the ER. He has had blood work done including a CT scan, everything checks outs good. He has not been eating that much and he says the gatorade makes him feel a little better. Activity level is shot this is what scares me the most. we are an outgoing family and all he wants to do is sit in one chair. I am getting frustrated because I can't diagnosed or seem to help. I have forced him to go to school. But when I look at him he looks ill in the eyes. Please assist