Newborn not gaining

Baby is 2 weeks old. breastfeeding is going well- my supply seems great (so much so that I have to use my haakka to reduce letdown and collect foremilk and I get 1-2 oz each time I use it, then match baby on and he gets a full feed still). Baby corrected latch issues we had on days 3-4 and we are fully off the nipple shield. He is feeding every 2-3 hrs on demand (sometimes more often) during the day for 30 min- 1 hr each feed. Night is every 4 hrs. Problem is he isn’t gaining as much as he probably should be.

Birth weight: 7 lb 12 oz

Weight day 3: 7 lb 7 oz

Weight day 8: 7 lb 1 oz

Weight day 10: 7 lb 3 oz

Weight day 15: 7 lb 6 oz

Pee and dirty diapers are plentiful. Yesterday he had 14 pee diapers and 6 poop diapers.

I bought a baby scale and did a few weighted feeds and he’s taking in between 1.2-1.8 oz every feeding I’ve measured.

He’s active and alert and strong during tummy time. He has grown in length and head in the past 2 weeks as well

What could I be doing wrong?? If it isn’t supply, or feed frequency, then what?? It doesn’t make any sense and I am at a loss. I struggled to nurse with my first but it was a supply issue plus he had low glucose so we supplemented in the beginning which affected things as well. I really thought this one was going different but somehow we are ending up at the same issue again and I’m so so frustrated.