I bought 2 bra's, and both had things I didn't like about them....
Then I bought this one: xxxxxxx and it's GREAT. It's expensive, but it's very comfortable, and supportive, and I wear it 24/7.
When I'm not wearing this bra, I wear Express tank-tops with the built in bra... those really help me too.
As for the sizing, I think usually I go up a size to be more comfortable and because I don't want them too small - however, I find with pregnancy clothes AND bra's, go with the size you usually go with. You want the bra to fit perfect, not too loose.
Pre-pregnancy I wore a large (or 38/40B/C) for comfort, and when I got pregnant I thought I should go up, maybe to XL if necessary - but the large is almost too big!