Tips for breastfeeding with heavier breasts??

Leilani
My baby is 9 weeks old and breastfeeds well enough but after initially latching, I have to hold my boob the entire time she feeds. Otherwise the weight pulls it down and she loses her latch. We nurse in several positions and it happens pretty much in all of them. Is this a latch issue or is it something I just need to accept with having bigger boobs?