5 month old , formula

When my son was born he didn’t latch on so hospital was providing Enfamil neuropro we noticed after every feeding he was spitting up a lot more of throwing up. So his pediatrician switched him to Enfamil AR he’s been on this since 2 months. Now, his poops are always hard and stuck to him when I change him. I’m wanting to try another formula the pediatrician recommended gentleease but he’s not crying or fussing I just want him to be able to pass a good poop lol

Any recommendations for what will help him poop because right now it’s just small little hard poops