The bad news is, they will go up more... I started out even bigger than you (F!) went up a cup size straight away, went up another cup size at the end of pregnancy, and ended up with a J-cup feeding bra. Seven months on it's finally getting too big. (I am also five foot two and so look like an upside down weeble...)
So, what worked for me? Didn't get out of underwired bras until 7 months into pregnancy - as long as the wire is flat on your chest and doesn't dig into the actual boob, they're fine.
I then bought a couple of bravado nursing bras from Blooming Marvellous (but you can get them all over the web - I also got a rather wonderful leopard print one to cheer myself up!). Although they're nursing bras, they're supportive and comfortable, and really worked for the end of pregnancy/start of feeding as, as someone else said. they are forgivingly elastic. And now I wear them in bed, so they were a great investment.
And then for nursing, the only one that works, I think, for the large norked is the Royce bra - John Lewis have it up to J cup, Bravissimo have larger sizes even than that. It's comfy, easy to use, comes in black. Also not a waste of money as I'm still wearing mine now!
Hope this helps and enjoy your pregnancy.