My son has been running a fever for 3 days now he went to the dr and was put on antibiotics he now has a deep cough and still is keeping the fever.i'?

Cough/fever: He may have a viral illness that is not going to respond to antibiotics. It is also possible the antibiotics hosen are not the right ones for his illness. If he has been on the antibiotics originally given for more than 2-3 days and is not getting any better, I suggest he go back to the doctor to make sure this has not progressed to pneumonia.