Waking Up to Breastfeed

We brought our daughter home today. She was doing perfect in the hospital with breastfeeding, but ever since we've been home I cannot get her to wake up for feedings. They told me to wake her up every 2-3 hours to eat, but it seems like she has a stomach ache and doesn't want to eat as much. We supplemented with formula around 5:30 and I'm wondering if that's maybe why she isn't ready for the breast again? Any tips? I feel like I'm going to end up giving up trying to breast feed