For 6+ months I EBF, but I am having to drop a pumping session or two because of work and will need to supplement. I have tried Earth's Best, Similac Advance, Enfamil Premium, and now Similac Sensitive and they all seem to hurt her tummy (except Enfamil which made her projectile vomit). I am only giving her 1-2 oz of formula with 5-6 oz of expressed milk for each of her feedings. I know formula is rough on tummies, but is this normal? I have not tried each of the formulas for more than a couple days because I hate to see her miserable so maybe I am switching too quickly? Any advice would be appreciated.