Re: Newborn constantly rooting around for food?
At 3 days old, a baby's stomach capacity is about one ounce. If he does fine with 2 oz, but 3 oz makes him puke, I would stick with giving him 2 oz, and feeding him more often, KWIM? Babies have a strong urge to suckle, so he may just want to suck, and not actually eat, after those 2 oz. I would definitely try a pacifier, and see if that helps.
Congrats on #3, by the way!
Trying-to-stay-sane mama to four boys (5/07, 10/09, 7/11, and 11/12)