My breasts have been SO sore the past few weeks and are growing rapidly!!

I really want to purchase a sports/maternity bra (just a comfortable one with no wires) as both sleeping with and without a normal bra is painful and I need relief asap.

My question is if I wear a 36D but it is slightly tight round my back but I am also spilling out of the cups, which size do I purchase for my new bra?

TIA x