Hi E., Welcome to motherhood! I am a nurse and mom, lots of experience with infants both professionally and personally. Is this the first artifical nipple you have introduced to the baby? Does he take a pacifier? If you dont introduce an artificial nipple before 1 month of age, the baby will often reject it for quite some time, if he takes it at all. Even with a pacifier, he may reject the bottle if not introduced prior to 1 month of age. It could also be that he does not like the taste of formula. It is not AT ALL sweet like breast milk. Breast milk is sugary tasting, like the milk left in the bowl after you eat the sweet cereal. Quite yummy compared to formula. If that is the aversion, it just takes time to integrate him to the new "flavor". Some babies are more "picky". You may want to try a "nuk" nipple or a playtex nurser with a "nuk" nipple. It most closely resembles the shape of your nipple in the babies mouth during suckling. The bag system is also cleaner, easier and allows alot less air in baby's tummy during feeds. It most resembles breast feeding from baby's point of view. The Avent system is also preferred over the typical plastic bottle system for lots of breast feeding moms. You may also want to use a "slow flow" nipple, or one made for a younger baby. Breastfed babies have to suck harder than nipple fed, the flow of milk through the nipple may be too fast. He also may not take the bottle from you, he associates the breast with you. He may take it better from someone else until he gets used to it. If you do the feeds, try laying him in your lap, propped up with a little pillow or boppy, or lay him next to you, avoid holding him in the cradle position or any position that is the same as you used during breastfeeding. Most importantly, keep trying. He will get hungry enough eventually and take the bottle. You can also try "cup feeding" with a medicine cup or a slow flow sippy cup. It's more work, a bit messier and you have to be very patient so he won't choke. Try not to get frustrated or upset, he will feel that and it will be harder and he will be fussier. Good luck.