my son poop I'm worried !

Alesha
Hello I'm a FTM & im worried about my son Nicholas! This is what his poop looks like ! Is this normal his poop been like this for a while now he on Similac pro advanced spit up ! & im wondering he has allergies because my
Mom has dogs & cats could this be affecting my son ? It's kinda mucusy aswell then again his poop didn't start being like this until his milk changed , could he be allergic  to his formula??? The cats or dog DO NOT BE AROUND MY SON AT ALL !!! I'm with him 24/7