You should go get yourself measured so you can be sure you're wearing the correct size. I was shocked to find out that post-pregnancy, I was not a 40C, but a 36DD. (I had been a 36C pre-pregnancy.) If there's a SOMA near you, they will measure you, and their bras are more supportive than the ones I used to buy at Victoria's Secret pre-babies. ;) Something the sales lady told M. that I hadn't known is that if your bra goes up in the back (rather than going straight across), you are wearing the wrong band size and you should go down a size at least. To compensate, you likely need a larger cup size. (Hence why I was wearing a 40C and should have been wearing a 36DD!)
In terms of milk drying up completely, I am not sure if it ever goes away totally. At this point, your cup size is probably the one you're stuck with.