I went to a professional bra fitters the other day and had a shock!
I know they say that 70% of women are wearing the wrong bra size but I was so sure it wasnt me. I'm VERY flat...barely an A cup but not a petite person really - a UK size 10-12.
Well, I'd been wearing a 34A but found out that I should be wearing approx a 30D!!! I was amazed! She said that women are often afraid to wear a bra that seems too tight around the band, but that it should be. Not uncomfortable, but tight. And because of the shape and width of my boobs they were a D, even though it looks like there's nothing there!
Since then I've been trying different sizes and it's worked miracles on the way they look and I've realised how stupid my 34As actually were, even though they looked fine under a top.