I wanted to comment that I just ran out and got a BE Band from Target (right next to my office) because my pants were starting to drive me crazy. I can still button all of them, but they're snug and tend to fall down because it's not comfortable to wear a belt anymore. Also I feel like my belly is exploding out the top of any pants I wear because weirdly, it has grown mostly from the top so far. Any squeezing from the bottom increases that feeling and makes me uncomfortable.
Anyway, I got the M/L and although I haven't worn it for long yet, I am really liking it! I unzipped my pants under it and used a hair tie to at least try and secure the button in case of wardrobe malfunction. I wore a 16W/18/maybe 20 pants prepregnancy, and this size seems to fit fine. Just FYI in case anyone was thinking of trying one, but was put off by the sizing available in the store. (They do have a L/XL for size "20 and up" online, but this one is pretty stretchy and not constricting so far. I risked going with a slightly more snug fit because I'd like to have a fighting chance at it being able to hold my pants up. )