I switched my son (three weeks old) from milk based formula because he'd been having issues, to soy…

I switched my son (three weeks old) from milk based formula because he'd been having issues, to soy based & his poop changed to like play dough pebbles kinda. I'm a little worried & not sure if I should put in a call to his doctor just yet.. (I think I'm gonna tomorrow if it doesn't go back to normal at all..) Any other moms experience this & know if it just passes with formula changes or..?