Hi there. I have H cups so was nightmare BUT I finally found something that worked - can recommend Elomi Bralettes. The band and for the back, is very very strong and held up my breast day and night. Very comfy to sleep in too.
Trying to get the word out to this network for any more busty ladies as my size has hindered my recovery.
Debra's in Sydney have them, as do Brava and Storm in a D Cup for online depending where you are.
https://www.debras.com.au/collections/elomi/products/elomi-downtime-non-wired-bralette-ash-rose?_pos=3&_fid=40f0d5d54&_ss=c&filter.v.availability=1
It was the only soft cup, wireless bra I could find with big enough options. They have them in black, grey and a new lovely pale pink colour. After a few weeks I then went to the Elomi sports bras as their cup designs have bigger wiring around the breast and under the armpit so doesn't cut into any sensitive flesh.