What can I do for a month old with constipation?

My baby is about to be 2 months old on the 14th she’s on both formula and breast milk, I have the formula only if I didn’t get milk pumped she’s mostly on breast milk. But she’s not pooping every day or every other day when she does go poop is only a little bit she has s doctors appointment on the 14th I may end up calling doctor in the morning.