I don't generally start threads simply because everyone else does such a good job of covering the bases. The one thing that has been a serious struggle for me with pregnancy though, is that in spite of gaining no weight so far and always having had pretty much the same bra size since 18 regardless of weight fluctuations, I have added five cup sizes since getting pregnant. I went from a 34D-36C to apparently a 34I-36H. As I've never been in that range, I really struggled to find bras that fit and have been in constant, sometimes excruciating pain. None of the maternity stores seemed to have bras that were big enough in my band size, and the cups seemed to run small even in the bras that were bigger cup sizes.
My mom asked around through her network of friends as I was completely clueless, but nearly in tears and because she is awesome. Someone turned her on to the site BreakoutBras.com. I would definitely recommend it, as first of all, I was able to properly size myself, and second, they offer really lovely extended sizes and although it's a bit of an investment, the prices were way better than I was finding when looking into specialty stores. I just got one of their offerings yesterday, and sweet relief! Right now they are offering 15% off. Just wanted to share in case there were any other ladies FREAKING OUT at how big their boobs were getting and didn't know where to start. They also have nursing bras and info at the end of their sizing page on how and when to size and buy them. Plus they're pretty. I know it sounds vain, but I've always taken great pride in my girls even if I don't really show them off a lot, so this has been a little traumatizing to my ego. 
Re: FYI... In case this can help anyone else
Thank you for posting this. I am small enough that finding bras isn't as big of a challenge, but at 25 weeks I've already gone up 2.5 cup sizes and it IS unsettling and bras ARE expensive. Ladies helping ladies is so great.
Formerly known as Kate08young
August '18 Siggy April Showers:
Married: 7/22/14
Baby L: 8/4/2015 August 2015 Moms
Baby E: 11/18/2016 December 2016 Moms
TTC #3 08/2017 BFP 11/27/2017.
Twin B lost 11/22/2017, Twin A doing well.
Formerly known as Kate08young
August '18 Siggy April Showers:
Married: 7/22/14
Baby L: 8/4/2015 August 2015 Moms
Baby E: 11/18/2016 December 2016 Moms
TTC #3 08/2017 BFP 11/27/2017.
Twin B lost 11/22/2017, Twin A doing well.