I hate it too! I've known for a while that I'm not wearing the correct size so I went to actually get measured. At the first store, I couldn't find an associate to help me....at the 2nd store, she measured me with the wrong size bra on, over my shirt, and only took one measurement all the way around. Then she told me I was a cup size smaller than what I'm currently wearing and I went in knowing that I needed to go bigger, not smaller!
So I found instructions online to measure myself, did it three times just to be sure. Couldn't find a bra in the new size in any store so I ordered it online...got it and it was ENORMOUS! My sister told me to just "go try some on" but the problem is that I don't know where to start! Obviously what I thought was the correct size is wrong but when I measure, I'm not getting the correct size either. It's so frustrating! Not to mention that bras aren't cheap!!