Hi, My 17 Months Child Suffers From Fever Frequently. It

Hi, my 17 months child suffers from fever frequently. It has been just 1 week that he was finished complete dose of antibiotic. Blood test was also done 1 week before and no infections was diagnosed. But again, he has fever up to 102 degree . I am worried why the fever is seen frequently? Can you please help me to find the answer?