my baby isn't eating properly

Okay I'm not sure what to do here..my baby is two weeks old and she's so good at breastfeeding, never had a problem. Tonight she's eating every hour and when she does nurse, she just seems to be sucking on a little bit of my nipple. It's really uncomfortable and I don't think she's getting enough milk that way. I've cried like five times since I started this last feeding (exhausted, uncomfortable, emotional) so I figured I'd see if you ladies can help. Every time I help her latch she gets mad and cries. She's exclusively breastfed. No bottle ever.