Breastfeeding Struggles

My daughter was born at 34w 3D and spent 12 days in the NICU. From the start we've been feeding exclusively breast milk from a bottle since she had endurance issues and incorporating more breastfeeding. I'm reaching a breaking point, as the lactation consultants from the beginning have said that she would likely get the hand of it by her due date. We're a week away from that and she is still struggling! Even after breastfeeding for an hour she is still hungry! It's intermittent, though, and sometimes she'll take 4 ounces! We attempt to breastfeed 3-4 times daily, but she is still so much weaker than on the bottle. I am struggling to keep up with pumping, breastfeeding, AND bottle feeding. Any words of encouragement or stories of your own preemies would be appreciated. Not giving up, it is very important to me to help her make this happen!