I'm a 46 D and I breastfed for the whole year. That was with my 3rd kid so needless to say they ain't all that firm and perky anymore and the nurses said not to hold them back. When I was nursing while sleeping I had my baby have him knees on my belly and had his back and head as far back as possible where he can still have a good latch.
I wear a 44DDD and the nurses kept telling me not to hold my boob back that baby will know when to breathe. Umm no thanks. As long as she's latched I'm holding it away from her nose. It's even harder with my right boob. It must be bigger. Lol