Is this okay??

So my 3 week old has only been eating for maybe 5-10 minutes and it’s a struggle to get to 15. Well today I did a weighed feeding at my house. My husband weighed himself first and then my baby before I fed him. He ate like 6 minutes off my right boob and 4 on the left. When we weighed him again it said he gained 4-5oz. So does that mean he drank 5 oz within 10 minutes? And is that okay for a three week old? He poops and pees after every feeding and he went passed his birth weight at his two week appointment. I’m just afraid he isn’t getting any hind milk with how quickly he eats on each side.

Picture of my little chunks ❤️