Every time I pump I get less milk.. help!

HH

My baby was born last Monday at 36 weeks so he is 9 days old. He was jaundice and ended up under the lights for 24 hours at the hospital then his bilirubin spiked again and was under the lights 2 more days at home. He was dropping weight and was having a hard time nursing because he was always so tired. I was told to start pumping. Well I started last night and had a great session. I’ve been pumping every 3 hours since then and my supply after every pumping session is getting less and less. I need help! What am I doing wrong? I’m doing skin to skin and we are trying the breast. He latches sometimes and may get a few sucks in before he falls asleep. I got over an ounce total from both breast the first session and now I’m doing good to half an ounce combined.