Breastfed Baby Poop

Im a first time mum...my baby has just entered 1 month old. Im exclusively breastfeeding, but via bottle. 2 days ago my baby didnt poop the whole day...The next day her poop was so massive it leaked her diaper and spilled partially on her clothes. I just recently find out its fine for BF babies to not poon as often. But mine looked like she is always trying very hard to poop, as though she is constipated. Today she didnt poop as well but she looks like she is very uncomfortable and trying her best to poop. Idk if I should be worried Is it the same for you guys?