Oh my dear Emily. I could have written your post. I'm a D cup ordinarily, and when I was pregnant, they just got bigger...and bigger...and firmer...and warmer...it felt like I was brewing hot chocolate in there.
They do max out eventually. Sometime in the second trimester, I think. They also kind of rest on your belly, once it swells up enough. And then after the birth, when your milk comes in, they will suddenly be VERY HEAVY too, and good support is a must. I wore these not very pretty, but very functional and comfy, soft cotton maternity/nursing bras by a company called Bravado. I was living in the states at the time and had to import them from Canada (the only example of any time I've ever had ship things in that direction!). A bunch of my American mom friends were using them too.
http://www.bravadodesigns.com/
One thing I will say: I wore a bra all the time, even in bed, and despite the fact that my breasts at least doubled in size, they are not saggy now. I nursed both babies (albeit only for five months each) and my little one will be five years old this year, so it has been a long time since everything has gone back to normal. I am very grateful, because I was positive my breasts would be hanging down around my waist by now. I don't know how much of a factor wearing a bra full-time was (there's a possibility it's just genetics), but I'm glad I didn't take any chances.
If it makes you feel better, my breasts went back down to exactly the same size they were before my pregnancy. Whew! They didn't stay huge. Yours probably will go back down, too.
Congratulations on the baby, by the way! It's a very exciting time, despite the unwieldy boob situation.
