My baby is 12 days old. He is currently on similac sensitive and this morning I noticed a foul odor and it sounded like he had watery poop. Sure enough. I opened his pamper and he had watery poop with mucus and some blood. He has experienced this in the past with enfamil gentlease and advance formula. He was doing okay on similac sensitive for about a week. Could it be the formula again?? His pediatrician scheduled him for a type of colon test and made us collect some of his poop so she can test it for a bacteria. I am overwhelmed and emotional.