Are you giving him infant tylenol & ibuprofen? Or either one? (both can be taken safely together, and are particularly effective for 2 things: dental pain and high fevers).
Just as a general reminder, DO go by weight not age, for correct dosing. If you have any Q's per the dosing, call the 24/7 nurse info line either through your ped's office or local hospital. They have the book/database that has the regular doses as well as the *max* doses (like for resistant fevers) for each weight.
((For those who don't believe in giving babies tylenol or ibuprofen for dental pain, I often wonder if they get dental work done without any form of painkillers? Or suffer headaches without? Hylands works for some, but it DOES make you high as a kite. Try it sometime you have childcare at the correct dose for your own weight. But DO make sure you don't have your baby and don't plan on driving or doing anything else dangerous. People usually hallucinate in addition to being rather goofy.))