Suggest Medication For Persistent Fever

hello doctor my son is 5 yrs old he had got fever wedneday took him to the doctor, medicine prescribed by the dfoctor was paracatemol and cetrizine still the fever didnt subside after the 3 days of medicine doctor prescribed him antibiotic cefeprox 100 twice a dya 4 ml after giving him this medicine also the fever didnt suside he gets fever around 102 after every 6 to 8 hrs has shivering and pespires alot .doctor has suggested that if required we will get ablood test done on wednesday , today is sunday should we wait for such a long time.