I have a very low supply because of various hormonal issues, so we are mostly formula feeding, but pumping gives me about a bottle or two each day. I'm starting to notice that my daughter is a lot fussier after the breast milk bottles though-- and she just threw up the whole last bottle. Not spit up, threw up. After the inevitable bath, she happily took a bottle of formula and fell asleep. I'm planning to freeze my milk for the next few days and see if she's less fussy on formula only. Anyone else experience the same thing? What did you do?