My Son Has Been Treated For Strep Throat With Amoxicillin

My son has been treated for strep throat with Amoxicillin and that did not work, and now with Cefadroxil. He is still running a fever and saying he is cold and he has been on the Antibiotic for a week now. I am afraid that he has a more serious condition like pneumonia based of his current signs and symptoms. Please advise.