Constipation

My little one hasn’t gone in 3 days counting today. We’ve tried just about everything, her diet has been a lot more regular food so that’s most likely why. But i dont know what to do and I’m worried about it. She is formula fed. She pees fine and fills a diaper no problem and has had gas, just hasn’t actually gone poop. Someone help! Obviously if she doesn’t go tomorrow we will take her to the dr. I just need some advice on the mean time