Well, we got an answer from the endo (Fellow), that, we shouldn't worry about his formula intake if he is eating foods, and behaving normally. So, I will feed him a "normal" diet, and not worry that he isn't drinking any bottles. Hard to do, but... no one can seem to give me an answer as to why he doesn't want to take any fluid via cup or bottle. I think he may be teething, since his upper gums are so sensitive.