I think it's a quirk with BF babies. I remember my pedi saying they can go up to a week (or maybe it was even 10 day?!) without pooping. I think the longest Spencer would go was maybe 4-5 days, and then there'd be a HUGE blowout. He actually did that quite often in the first 3-4 months (not pooping for 4-5 days). I wouldn't worry about it just yet.
I wouldn't worry yet. As long as he doesn't seem uncomfortable then he's probably fine. If he does start to seem uncomfortable then maybe help him by pumping his legs, etc. J often went a couple of days in between poops and then, like S said he would have big blowouts. Lucky us, huh??
Right around six weeks was when C started going longer between poops and didn't poop everyday. Like the other posters, when he does poop, it's usually a massive blowout. I wouldn't be too concerned about it.
Natalie was totally regular until about the 6 week mark...then she would go a week without going, She actually started going every week on the same day, which we named "poop day" and that lasted about 2 months...poor kid.
Re: Would you worry?