Move over Pamela Anderson

I need new bras. I only realised this when it became apparent that instead of heading straight to the fridge, the first thing I now do when I got home each evening is take my bra off. This is not a usual occurence for someone with a petite set of breasts. And it isn't so much that the cup size has grown (although I'm sure that will happen once the little one shows its face), but that my ribs have stretched and consequently the strap of my bra digs in with gusto from about midday.
It's amazing how people tell you this will happen but I, (worrier extraordinaire) needs to do a Google search for 'pain in rib area' before it clicks that there is nothing medically wrong, it's just that my old (well, just-pregnant) 32C numbers, no longer cut the mustard. In fact, just writing about it now, is making me want to unpop those hooks and let it all hang free. I won't, of course, because I'm in the office and wearing a slim fitting top, but wow, how nice it would be to not feel like I'm being slowly strangling myself around my lungs.
The question is, what size do I get? Do I buy for now, when my boobs are still a 'normal' size, but my back is Jeff Capes size, or invest for later, when my back shrinks (I'm hoping my ribs slot back quite quickly) but the chest up front is rather enormous? Mmm, the dilemmas.
I think I'll go to Marks and Spencer and let the woman in the fitting room guide me. Or maybe I'll head to John Lewis. Wow, my brain is already so mushy. I can't even make a decision between two department stores. Help, people, I've lost my intelligence. Let's hope it comes back, at some point soon, when the 32 inch decides to show its face again.