Hi and thanks for the query,
The presence of fever and cough or signs of a respiratory infection could imply a bacterial infection. It can however be bothersome to take drugs and still have symptoms.
Resurgence of the infection could arise because of the following reasons:
1. Inadequate duration of treatment
2. Inappropriate antibiotic
3. Resistance to the causative organism
4. A complication like lobar pneumonia
or pus collection. Its compelling to have a clinical reevaluation and probably a chest X ray
and complete blood count
I suggest you revisit your pediatrician
for a complete review.
Hope this helps and best regards,