Both breasts or one?

A little background..

My baby boy was born 6lbs 3oz. We left the hospital and he weighed 5lbs 10oz. At his weight check 2 days later he weighed the same. 5 days after birth he weighed 5 lbs 12oz and now, 13 days old he weighs 6lbs 1 oz. 👏🏻👏🏻

My first was formula fed due to issues with breastfeeding but I'm planning on exclusively breastfeeding this one. He does take a bottle now and then but that's so daddy can feed him or if he goes to grandmas for a few hours. He has had absolutely no nipple confusion between the bottle, Breast and paci. It's great! Such a better experience than my first.

My question though is, he only nurses from one breast before falling asleep. I think he's only eaten from both breasts once and it was one full then a couple sucks from the other and he was out. When will he start to eat from both breasts? I just want to make sure he's getting enough. Sometimes he gets too much and throws it all up. I'm having a hard time gauging his intake. Any tips?