Strep test at patient first negative.white spots,fever(gone last night).swollen glands.said strep anyway.gave antibiotics.could it be mono?

Maybe: rapid strep was negative but culture was positive? Mono can be a cause for these symptoms.

Possible: the rapid strep test is pretty accurate and false negatives are not common, meaning you probably don't have strep. Sometimes a second test is sent for culture of strep if the clinical appearance indicates strep. Most likely you have a viral throat infection and mono is one of those . It can be tested for and diagnosed very easily. May want to contact your doctor if concerned

Possible: But if symptoms have cleared so quickly on antibiotics, it may be strep. If you fail to recover, have a mono test down. Just as a caution, some antibiotics will give you a rash with mono. All the best.

Sore throat: I would suggest go ahead with antibiotics for 10 days . The lymph nodes subside in few days . If persist , get checked by the pediatrician again . Unlikely infectious mononucleosis , as this is not the age, course of disease is more chronic .