My baby girl is 10 weeks old...today is Tuesday I changed her formula Sunday because the formula she was on before made her spit up a lot...since Monday night she has had diarhea..really runny poop...it went from a little loose and green to yellow and really watery! She doesn't have a fever and she seems to be eating and sleeping ok but her poop just gets worse and worse...should we go to the hospital? (her pediatrician is closed and they charge $13 to talk to the nurse on call)