bad formula making my baby sick

I bought infacare stage 2 milk from the toys r us in 3 rivers the expiry date is only in September 2015, how ever when you mix the formula now matter how much you shake the bottle it still looks like the milk is off so i thru away the 1s bag opened the second bag last night and when i gave the milk to my baby she vomited the whole night, I cant take the milk back to toys r us as I don't know where the slip is, but i do feel that there is something wrong with this box of milk my baby never got sick from infacare.