He nursed 4 or 5 minutes pre breast. He would nurse for about 10 minutes total. Your milk might be flowing faster than some women.
Babies grow at different rates.
I too suggest nursing more frequently, or pumping inbetween feedings to increase milk supply, if you do not have enough milk. However, your baby is gaining weight so is probably fine. I would not suggest a supplement unless you need to, because God designed mom's molk to be what the baby needs. Other things do not compare. My son nursed every 2 or 3 hours.