B.D.
Did you ever pump milk and give it to him in a bottle? My daughter was very similar. What my pediatrician suggested was to add a little bit of imitation vanilla (doesn't have the alcohol) to the milk and give it to her in a bottle and then gradually wean off the vanilla. That worked wonders for us she was off the boob and drinking whole milk in about a week. Breast milk is very much sweeter than whole milk and formula and he's accustomed to that. Plus he's used to sucking in order to get his milk. It could also be that maybe he isn't ready to wean even though you are. Does he have a favorite toy that comforts him? If so give that to him when he drinks from a bottle or simply hold him close while he's drinking from the bottle. Good luck.