This seems so silly but for decades I have been wearing bras that I thought fit. Recently, since getting implants, I decided that my boobs were not happy in any bra that I bought. So I decided to head over to Victoria's Secret and have someone actually fit me for a bra. We do it with swim suits, jeans, dresses, shoes, ect but it seems like bras are a little too intimate to try on (or so I thought). Well it didn't take too long for the bra fitting lady to whip out a bra that made my ladies look great and comfortable. And I learned a thing or two. I learned that the reason my bras were gaping at the arm pit was because the cup was too small and I learned that I needed to stick with a smaller band size. I've always assumed that I needed to wear a 32 since I wear an XS in most things, but the problem is that a 32 is not easy to find (especially on the clearance rack at Target!) so I'd compromise with a 34 in a smaller cup size. Bad idea! Turns out my actual measurements are for a 30dd. As you can imagine, this size is not easy to find but a 32d is acceptable (a 34c however is not, as I had previously thought). I've also found that there are several European retailers that sell the smaller band sizes like (www.figleaves.com which has a great outlet section) and I'm giving them a try.
Point of the story: if you haven't had a bra fit recently GO & DO IT. It may just change your profile and definately your comfort factor. I know Vicotri'as Secret & Soma Intimates have trained staff that do fittings and propbably several other places too.
Have a fun weekend.