how baby feeds when pumping vs. nursing

How do you guys know your baby is full when breastfeeding? When I pump and bottle feed, my baby actively drinks.. I notice he can drink 4-5 oz and go to sleep till its time to eat (which is 3 hrs later)... but when i'm nursing I feel like he doesn't drink much and falls asleep instantly, then wakes up soon after wanting to eat... does nursing just calm the baby and make him fall asleep faster or something?? When I nurse I get zero sleep to the point I can't function anymore.. so I really need some advice.