Third baby, first breastfeeding struggles..

So like the title says, this is my third baby and the first time I’ve had any struggles breastfeeding. He lost weight after birth which I know is normal, but he didn’t gain enough weight at the first weight check and we are going back Monday for a second weight check. I’ve been told to supplement (breast milk first and formula second or if breast milk runs out) every 2-3 nursing sessions. The pediatrician also clipped his tongue tie to see if that’ll help.

My nipples hurt but I’m only 9 days in and they hurt with my last two. It just seems like he always gets so sleepy on the breast and/or doesn’t effectively suck or suck for long enough before falling asleep? He takes the pumped breast milk in a bottle like a champ. It’s making me worried because I would much rather breast feed than exclusively pump and don’t know if I have the patience to do so with my two other kids.

When I do pump I am pumping plenty so I don’t think it’s a supply issue.

Any tips? 😩