M.J.
I had the same issue with my little one. He actually cried the first time I tried giving him formula! I did the same as what some of the other posts mentioned. I mixed in formula with the breastmilk gradually until it was just formula. I started with one ounce for the first few days and gradually increased the formula every few days. After a while the baby will get used to it. (if not trial some other formulas)