My Son Is 3 Years Old I Took Him To

My son is 3 years old I took him to the doctor about 3 weeks ago he was placed on antibiotics for a virus. He was running fever, runny nose, coughing. Nothing crazy. He was placed on the pink liquid amoxicillin for 10 days we completed those and he was good for a few days now he is having all the same symptoms all over again? Could he have been mis diagnosed? Nit sure what to do.