Go to hospital right away. Once you get in, there will be lots of painful tests, urine, blood, etc. ordeal for the baby but no choice.
39.3 is not very high, don't worry too much, and for little babies temperature around 37 is normal.
TYLENOL only helps to drop the temperature but it doesn't cure the cause of the fever, which in many cases, are infections (urine infection in our case).