I agree about feeding your baby also if she is not keeping it down it will effect how much she eats. So make sure you hold her upright for awhile about 30 minutes afterwards to make sure your baby is keeping most of it down. It depends on if it is growth spurt time too. Every so often babies sprout a bit and they do some heavy feeding. If you need more help from me just email me at email@example.com or cafemom.
Are you nursing? It takes some time to get your milk supply going. Does nursing hurt? It should not (if he is not latching on correctly, it might hurt you and he won't be getting much). When he is not nursing, let your pump work on your breasts even though no milk may be coming out. It will eventually build your supply up. Also drink water every time you nurse.
I did the same thing with my son when he was a baby. My ped. told me that he was doing that becuase I feed him all the time. He was gaining weight too fast and I wasnt realizing. I would ask your Ped. if that is the case. I know womeone else who did that too. I mean if she is REALLY hungry, then ofcourse feed her. God Bless hun, I hope this helps.