1 one month old constipated we are on the 2nd day with no poop. Switched formula to gentlease. Any remedies?

When my son was constipated at 2months I took him to see a doctor at his pediatrician office and the doctor he told us to use a little bit of Perm juice mix it in with his formula and it helped him not be constipated.

Our dr had us put the smallest ammount like 1/4 teaspoon of apple juice in my sons bottles to help. And then warm baths and lots of tummy massaging and leg bicycles