feeding problems

Naomi
Hey mummy's, my baby is now 2 weeks old and on a night she is constantly feeding. Last night she was latched on from 2am until 7am.. with only brief breaks in between. My nipples are super sore and as you can imagine I'm exhausted. I'm worried she's not filling up off me. But when I try her on sma formula she throws it straight back up. Any advice?