I had a 36-week baby on March 28, at first, being premature she had trouble with the latch, she just wouldn't do it, then at the hospital they showed me the breast shield trick, and it just did the whole difference. I used breast shields for two weeks because, even if I tried, she just couldn't latch. Then one day, she was able to do it, and we got rid of the breast shield. Now I'm exclusively breastfeeding and bed-sharing (which makes the difference for night feedings, you are not exhausted all day and your LO eats more often).
So I recommend you try the breast shields and keep up with the good work. Trust me, there is nothing like feeling your baby feed from you, and know she's thriving. GO FOR IT!