@Gabrielle I have no idea! 😭
Have you tried to pump that side to see how much comes out?
One side is usually a better producer. I exclusively pump and my right produces double the left, and that’s with me working on getting the left up too!! Maybe try offering it second so he’s not as hungry, maybe he’ll stay on longer instead of getting frustrated? You can massage/hand express a bit to get the milk flowing before he latches too. If you have a pump, pump on that side if he won’t drink from it, should help bring your supply up
Why do you think it’s not filling up? Besides now him being fussy with it