11 months old sick

Hi mummies, my 11 month old baby sick since 5 days ago. Was having high fever (highest at 39.8). Fever gone, came the cough on the 3rd day, but then on the 5th day which is today, fever came back. Baby lethargic, not drinking milk. Seen pd 2x (on the first day, and 3rd day to take cough syrup. What shld I do