Formula and breastmilk fed poop


My little one is getting breastmilk during the day and formula at night time (due to a drop in my supply) I have been doing this now for about 2 weeks and it seems that it takes days for him to poop and when he does it’s because I have had to help stimulate him to go. Anyone else formula and breastmilk fed and if so how often did your little one poop? He’s 6 weeks old. When he does go it’s not hard. It starts a little formed but soft then the rest is a blow out. I mentioned this to his pediatrician and she didn’t seem concerned. I just feel like he gets really uncomfortable after a day or 2.