My 3 Year Old Grandson Has A High Grade Fever

My 3 year old grandson has a high grade fever for 5 days now. He was taken to the doctor who diagnosed strep and prescribed augmentin. He complains of stomach pain, headache and being cold. My daughter took him back to the doctor Tuesday he was tested for the flu and test was negative the doctor though prescribed arritomyzin. He still has a high grade fever that only breaks when given ibuprofen or Tylenol. What do you think?