My Son Age 5 Started A Fever Monday Afternoon, By

My son age 5 started a fever Monday afternoon, by Monday night he had a slight rash. Today the rash is worsening and he still feels hot to the touch. He's had benadryl, Tylenol, and advil as suggested by the pharmacist. Now he's developing white spots in his mouth and says he feels like bugs are crawling on him making him itch. Should I take him to the emergency room?