My little guy has been on the regular similac from day one he's 10 weeks old. The past week he's been spitting up a lot more and having extremely runny poops. after he eats I can hear is little tummy rumbling like its upset. He's not fussy or acting different just his regular sweet self. Should I switch formulas? And if I do do I use the similac for Lactose intolerance or the one for easier digestion? It may seem silly but it sounds like they do the same thing. But could this also pass? I don't want to give him something he doesn't need that might actually make him sick..?  His bottles and everything are always clean and sterilized. Help!