Bel,

You're spot on, Charlie is on cow's milk and for the first few days had some runny poos. After that though, his tummy got used to it and he's fine now. He doesn't have more than 2-3 bottles a day though.

If he seems unsettled by it, maybe try half formula, half cows milk and slowly decreasing the formula over the course of a couple of weeks? My ABA counsellor suggested that for Charlie but he ended up on straight cow's milk in the end.