Poor thing. MAM bottles and Heinz Nurture Step 1 (whey based) worked best for my bub. I had initially put her on S26 and she would bring that up all the time and just didn't sit well with her at all. When I switched her to Step 2 (casein based) she had explosive poos, after every feed and then some, just like your bub. When I read your post my first thought was that it was a lactose intollerance. Karicare has a great lactose free formula at a good price (my local Terry White chemist has the best prices on formula). It made a difference straight away when i tried it after having her on step 2 before switching back to step 1. Worth a try...good luck!