My Son Has Been Having Symptoms Of Swollen Glands, Swelling

My son has been having symptoms of swollen glands, swelling of throat and sore throat along with body aches x2 days. In the last 12 hours has been vomiting with diarrhea. When is it advised to go in to get IV fluids. He went in to 2 clinics regarding the above symptoms and a strep test was negative and CBC was negative. Thanks!