My 12year Old Son Was Given Amoxicillin For A Throat

My 12year old son was given amoxicillin for a throat infection. He started today and has had a fever of 102 since Friday. Dr had told me to call him for a medicine if his fever continued over the weekend, so we did because fever and pain persisted. I looked at his throat and there were white spots. Is this normal?? Is the amoxicillin ok for this??I