Prebiotics

Amber • If you don’t eat your meat, you can’t have any pudding. How can you have any pudding if you don’t eat your meat?
My 4 week old has been prescribed Nutramigen because she has reflux and dairy makes the reflux worse. I had to stop breastfeeding, and now that she's just on the Nutramigen she has been constipated. She didn't have trouble pooping when she was on formula with prebiotics so I was wondering if anyone had a recommendation for a prebiotic?