My 7 month old baby has had a fever for over 72 hours. After how long should I go see a doctor?

The fever appeared on Friday PM (38.6) goes down a little with Tylenol but need to have Advil too to disappear. Saturday evening fever 39.6 we consulted the emergency room for laryngitis with stridor at rest which left after 20 minutes in the cold outside and we were sent home. Since then it's always close to 38.5/39.0 if no tylenol/Advil. I do saline and blow baby's nose every 4-5 hours, he coughs very hollow, is not dehydrated, we hear a light wheeze when he breathes and cries every hour at night since. When should I go back to the doctor?