Similac alimentum

I have a 9 week old son. He has been on enfamil gentlease since he was probably 3 weeks old and he’s always been gassy but a normal amount. The past two weeks he’s had a really rough time and screaming in pain. I took him to his pediatrician and they put him on famotidine for reflux but it hasn’t really done anything and I’m starting to think it’s his formula. Does anyone have any experience with similac alimentum? My friend gave me some cans and some bottles of the ready to feed. I’m gonna try the cans first bc it’s less expensive but I’ve heard babies do better on the ready to feed a lot of times. Any advice? He goes to the pediatrician Monday for his 2 month appt but I can’t wait until then to switch him bc I’m so tired of seeing him in pain and am hoping to find a fix.