Child has strep and very mucusy cough that began after starting antibiotics, could this be pnuemonia? still has fever after dose 3 of antibiotics

See doctor now: it is not clear that your child has strep pharyngitis or not? Was it confirmed by rapid strep screen? You said he had 3 doses or 3 kinds of antibiotics? Any way he is still running a fever. He needs to see the doctor ASAP. Maybe more blood tests or CXR need to done to make a correct diagnosis and followed by appropriate treatment.