yes. mine was on mixed feed and did not poo everyday as well. longest record 8 days without poo. checked with pd, she mentioned to see if baby stomach is hard/bloated. if got fart, should be fine. she mentioned to go back if 10 days no poo. but if you're worried, no harm paying your pd a visit to check. :)
Maybe can try to give Gripe Water. But do read if can give baby below 2 mths. I think can bcz Im not really sure at what age exactly did i give my newborn Gripe Water when she cnnt poop.