How often do newborns poop?

My daughter is 2 weeks old. When she came from the hospital she was going regularly. She is formula fed (similac) which we changed to (enfamil) she has been struggling to pass stools. Yesterday I had to help her poop with a rectal thermometer. How often do newborns poop? And is it normal for her to be straining but only passing gas and nothing else? I would ask her pediatrician but it’s a Sunday and I don’t see her till Tuesday.

Any response is welcome

Thank you 🙏