what's the best way to change formula for a 2 month

do you mean formula brands? or like from regular formula to Gentlease?

My son is on Gerber gentle but the Dr wants him to be on Similac alimentum

I just straight up changed. I didn't do anything special. My son was on gentlease and switched to soy. I saw an immediate difference, he was 10x better!

Okay thank you .