Cow's milk

My son is turning 9 months the beginning of November, and he has had problems with digesting formula since he was a newborn, It constantly has upset his stomach, constipated him, made him spit up and fussy, any thoughts on switching him to cow's milk this early? My mother and MIL both said their kids were switched around this age, although times have changed and they recommend giving it till they're one year old, I am considering it, Has anyone switched this early? He has been on several different formulas and the change really takes a toll on him and they're talking about switching him yet again, I just don't want to put him through this again.