welcome to hcm
its better to shift to any paracetamol
250 mg 6th hrly instead brufen
.can you please mention the antibiotic you are using?
you have to do some blood tests like tlc,dc,mp for pf and pv, widal also.better to rule out other causes also.
if need he may need bit higher antibiotic. and this should be taken under the guidance of pediatrician
. for cough you can use cough syrup prescribed by your doctor.rashes will come down once infection subsides.also he can use a multivitamin