This appears to be a virus such as the one that causes measles or fifth disease
. -Both these are viral rash
associated illnesses that resolve on their own within 7-10 days. You need to visit his pediatrician
to show him the rash and get a confirmation, but this looks like one of the rash-associated viral illnesses.
In the meantime, give him plenty of fluids, light food and stick to one fever medicine, either ibuprofen or paracetamol
, but not both used alternately = this is of no use.