Child is on antibiotic, amoxicillin 7.5ml bid. has three days left and has started to run fevers again. had an outer and middle ear infection. why?

Fever on abx: Fever while on antibiotics can be something as simple as he has contracted a viral illness that is not responsive to antibiotics at all (not that uncommon a week after you have been in a germy doctor office) to something more serious like development of a resistant infection that is not responding to the Amoxicillin. You really need to make a follow-up visit with your doctor in the next day or two