FÓRMULA HELP!

Sarai • мαтєσ 👶🏻
I was breastfeeding for the first 2 months but now I have stopped and started giving My baby Enfamil Gentlease but when he poops his in pain and sometimes doesn't even poop that day , what can I do? Should I change his formula? If so, what kind of formula do you guys recommend? Also has this happen to one of you?