I'm primarily BFing, but we do supplement some if I haven't been able to pump enough or in time for a feeding. And I don't have a freezer stash either for the days that I am working, so DH needs some formula on those days. So far we have only given him regular Similac Advanced that were samples. I have other samples of Similac sensitive, Enfamil newborn, and regular Enfamil infant. Do you think its ok to give him these for the occasional bottle or will it upset his stomach? So far he doesn't seem to care if he has BM or formula and it doesn't seem to make a difference in his diapers or make him fussy or anything, but I don't want to change that or push my luck. Once I had to switch Owen to formula, I only gave him one kind of formula and I was too nervous to try and change him to anything else. I just don't know if that was really necessary or if I was just being an overly cautious first time Mom.