I had a similar situation (with different doctor) when my bb had chicken-pox at 3 1/2 months old. After he had taken the medicine for about one day and kept crying excessively, I realized he was over-dosed (by researching on the internet, he should take 3/5 of the dosage suggested by the doctor). When I called the doctor to confirm, he said chicken-pox itself is hard to kill .....
Anyway, we still keep seeing that doctor. He seems to be pretty good most of the times except for that time. We just need to be very careful with the medicine given to our bb next time.