How has he been feeding? Jazz got 'diarrhea' a few times, green and frothy (eww I know!), and apparently babies get that sometimes if, when they are feeding, they are taking the foremilk mostly and not enough of the hindmilk. I was swapping sides before she was done and I guess she wasonly getting foremilk, I wasn't giving her enough time to get to the full and creamy stuff. If he doesn't seem 'off' could this be a possibillity?