Supply Question

JMC11511

LO is 3 weeks 1 day old. He eats every three hours (give or take about 30 mins) and usually eats a total of 25-30 minutes (10-15 minutes on each breast). We have to really work to keep him awake especially at his mid afternoon and late night/middle of the night feedings. My question is this, how do I know whether he is getting enough milk at each feeding? He usually goes to sleep immediately after the feeding so I assume that if he were not satisfied he would fuss/cry. Also, we bought a baby scale and have been weighing him before and after each feeding. Usually the difference is about 1-2 ounces. We weigh him naked. Tonight I realized I had a clogged milk duct in one breast so I had him nurse on that side and then pumped to see if I could get it unclogged. When I pumped, barely anything came out. The other side yielded about an ounce, which made sense because he had not nursed on that side. I'm just worried that maybe he's not eating enough or I don't have enough milk for him. He is also 37 weeks gestational age. Does anyone have any experience/feedback with this? TIA!