If an underwire is getting uncomfy, you could always try getting a couple of cheap wire-free bras to get you through? Maternity bras are pretty well-designed these days, the ones I bought were made to wear from conception through to birth and then all the way to the end of BFing as your boobs grow and then deflate with BFing Hot Milk makes some really gorgeous maternity bras that are all lacy and girlie but give you all the right support you need, check out their site and see if you have any local stockists
I didn't swell *too* much while pg and found underwired, padded push-up bras pretty comfortable right up until my milk came in, but I still wear my maternity bras to bed to combat the sag factor lol. I just got a couple of cheapies from Kmart that look like sports bras but have the clip-down cups for feeding, and they've lasted me nearly 3 years!

I've found that maternity bras are well worth the investment no matter what stage of pregnancy you're at, because instead of 3 hook-and-eye closures, they have nine or ten, allowing for much more expansion of your breasts, and then you can tighten them up again when your supply settles and your boobs go back to normal a bit. Good luck finding the right ones for you, can't hurt to go shopping now and see what's on offer HTH