My 6 year old has had strep 5 times since February. They are thinking he is a carrier. He has been on Penicillan twice, Augemntin twice, and now is on Clindamycin. He has been on it for 7 days and tonight began complaining of a sore throat? He usually just shows signs of bad sinus infections. Should I be worried is this a side effect?

Are you seeing an ENT (ear, nose, throat) doctor? If not, you may want to see one. I would ask his treating doctor about his sore throat rather than strangers on the Internet. We can't diagnose here.