My 3 week old just threw up after a feeding. Some people say it's because they can be overfed, however, it was two hours since my last feeding, and she started to cry and show signs that she was hungry again. During the feeding, she was a little fussy and crying off and on, and when she was done, I was going to burp her when she threw up...(eventually twice). She seemed relieved after throwing up, and stopped crying. Anyone going through the same thing? or know what this can be?