A sales lady measured me right away, telling me I was a 34 C. So you think you know what a D cup looks like? I know it is a bit late to comment but, I am fourteen and I have had trouble with my sizing. Maybe write to some morning shows and try to get the backing of a company like bravissimo? Hope that helps a bit!
If your bra cup size is too small, you may find the wire is sitting on breast tissue which could be hurting it.
By the way, I just wanted to say that I really appreciated this post. Support us on Patreon! This is a brilliant post! I disagree with the idea that anything bigger that a triple D is fake. Could you post a new link. It does sound like your band size is a little too big and your cup a bit too small, although it could be that your bras have gone a little worn over time. I have had to show people another one of my bras with my size on it.