As long as he passes urine 7-8 times a day that means you are having sufficient milk. You can keep an eye if you are changing 4-5 dipers or 7- 8 wet langot in 24 hours. Rest pooping in 3 days is quite common.

I think it's completely fine until the potty s color change or baby having difficulty passing stools. my baby too had such issue and my pediatric said nothing to worry. i just kept hydrated.