I'm not sure where you got measured, but I went and got measured at a maternity shop and the lady really knew what she was doing. The size she put me in, for the first time, actually fit properly.
I am a 38 DD.
MY problem is not "falling out" of bras...even if I get one that is the "right size", if I lean over, whoops, there I go.
However, I JUST found a bra that I absolutely LOVE...and believe it or not, I found it at WalMart for 12 bucks. I believe the "brand" is called "Sweet Nothings" (in fact, I just had my seven year old look for me, because I don't feel like taking it off to check...and NOW she wants to know what sweet nothings means...yeesh...). The coverage and support on this bra are AWESOME. It is white with pink lace around the top of the cups, but the lace is sewn literally on the cups so it's not itchy or against my skin. I can jump around and bend over and this bra holds it all!!
(I also hate Victoria's Secret for bras. In my experience, they make bras for teeny little teenagers or women with no boobs.)