J.A.
My first thought is that your daughter is teething. My son began doing the same thing around 4 months. He would nurse for a minute or so, take a break and fuss and then go back. He is now 5 months old and his teeth still haven't popped through, but I can tell when they are bothering him, he doesn't sleep or nurse as well. The pulling off decreased my milk supply too. Another thing I experienced with my older son is that he became more comfortable with the quick flow of the bottle vs. the breast. Not sure if your daughter uses a bottle at all but my son became frustrated with waiting. With my 5 month old now I only nurse him and he only gets bottles at daycare. Hang in there!