Help! Is he eating enough?

FTM. LO is 3 weeks 6 days. He wasn’t gaining a lot of weight for the first week and had latching problems, so I switched to pumping for a bit so that I know how much he was eating, then he was gaining decent weight and doctor was happy during the 2 weeks check up. I just switched back the EBF this week.

The feeding session will range from 15 mins in total to a good 30 mins. He is usually spend more time on one side. Way less time on the other. For example, 10 mins on the left, 5 mins on the right.

When I switch side and he pulls away, I would try multiple times to get him latch, he would cry and be fussy. If I go with his flow, try latch once or maybe twice then stop when he is really pulling away from my boob, he normally is content.

I see moms on this platform always saying their feeding session is at least 15 mins each side. That makes me wonder if I am underfeeding my baby…I do have a decent supply..sometimes i would even spray my baby, and most of the time when he pulls away, the milk will get on my pants and wet my pants real fast. He still spit up here and there.

How do I know if my baby is eating enough? Or how do I know my feeding session is too short?