What Causes High Fever And Diarrhea In A Child?

My seven year old son has had a high fever for two days. 104. He also has a terrible stomach ache with nausea, but not diahrrea. He has had a loss of appetite for several days before and still does. He has also complained of a terrrible headache even before the fever. Also, he has complained of his legs aching. He is on cefdnir 1 1/2 tsp. once daily. started this five days ago. He is very clammy and can t even sleep well. His doctor ordered blood work today, but won t have it bavk till tommorrow around noon. Also his neck bothers him when the motrin is wearing off, He has had some grapes and a small grilled cheese and kept this down, but the stomach ache is still present. He will eat a little for me before I give motrin. I m scared I need to take him to the ER. Any suggestions? Also, three weeks ago he had a terrible congested cough and sinus issues. He was prescribed augmentin for that and the cough did go away, but he clears his throat constantly. The doc did look at his tonsils and they are swollen, but not pussey he said. He also did a flu nose swab and it was negative. Should I go to the ER? He is really sick.--THANK YOU FOR ANY ADVICE