How Can Mucus In Stool Be Treated While On Enfamil A+ Gentlease?

Hello My baby is 3 months old. When we came home from hospital when she was a few days old her poop became hard. So I transitioned her to Enfamil A+ Gentlease from Enfamil A+. Then a couple weeks ago her poop becam explosive so I thought maybe she was ready to switch back to a regular formula. So I started the transition and her poop became mucus so I switched her back to Gentlease. It’s still mucus and I called her doctor and the nurse said to alternate formula each feed. There is no change. She still has a lot of mucus in her poop. Please help