Asher I am normally a 36HH, so not having underwire is a new thing for me, but I have actually been amazed at how supportive the one I have has been. I got it from Bravissimo, and although the shape is a bit rubbish, it definitely holds me in place, so could be worth a go.
I remember when I had my first pregnancy years ago, I got told that underwires could cause cysts in pregnant women. No idea if it is true, but I moved on to soft cup as soon as I got my BFP, and am definitely more comfortable. The only thing is the one I got was about £28, which I just can't justify if my size is going to keep changing, so I'm giving the Miriam Stoppard ones from Debenhams a try (if they ever arrive!)
For maternity clothes, I have been on eBay. I've got 3 Isabella Oliver wrap dresses (the same dress in 3 colours because it's amazing) and they are really comfortable. I also got a dress from ASOS maternity which is so pretty, and they all just look like normal dresses. I was going on the principle that a size 16 maternity would fit me as a fat 18, and when I lost weight they would also do me for maternity, and it has worked so far. JoJo BeBe Maman is also lovely. If you'd prefer brand new stuff, I've heard that New Look and H&H Mama are really good