Please help - newborn not pooping

Today will be day seven since my ten day old baby has pooped. He’s been exclusively breast fed and gaining weight on schedule but has yet to have a mustardy breastmilk poop.

Despite the weight gain I’m really worried I’m not feeding him enough or that something is wrong. My older child once went a similar amount of time without pooping but was a few weeks older. Baby is still passing gas as normal and can be typically fussy when he needs to pass wind but aside from that has shown no discomfort or bloating.

One possible cause I’ve been wondering about is if I had a lack of colostrum due to initially tandem feeding with my 20 month old as I read that colostrum acts as a laxative and is why most breastfed newborns tend to poop with each feed.

Has anyone had a similar experience???