You might not realize that your supply is low.. and the baby isn't getting their tummy stretched out to grow.. thus, they often can get tired, which you might mistake for being full.. but surprise, they aren't even close to being full! This happened with my son.. he was born with a tongue tie and low and behold, he got tired before he got full. He never lost weight, but he wasn't gaining the way he should. I began to pump and realized my supply was SO low and never knew! Sometimes pumping once can make you realize how much or little your babe is getting!