Baby doesn’t always poop every day- normal?

He has an appointment coming up (so I’m gonna ask them about this too lol) and I know they said it was normal when he was younger, is it still? He’s turning 7 weeks tomorrow and is breastfed for reference. He’s got plenty of wet diapers, but sometimes will skip a day to have any dirty ones. He seems to be gaining weight fine but he does grunt and wriggle around a lot as if he’s trying to pass gas/poop quite often. It happens after every feed and often in between them too and he strains hard enough to get red in the face sometimes. Oh we also burp him after every feed of course! I do tummy massages and bicycle legs but nothing seems to happen. Could he be constipated? I have no idea how to tell because when he does poop it certainly doesn’t look like he was constipated?