Hi Amanda I myself don't take my own measurements but I go to a bra shop to be fitted in fact on of my best friends works for a bra shop also you can go to a department store and get a fitting and the fitting always matches the bra specialty shop. Also it is entirely possible to a DD but not look like a DD I myself wear a G cup but I look like I might wear a D possibly a DD...LOL.
Suggestion if you ever decide to wear a bra don't try a bralette. You don' t have to be measured for a bralette they come in SML
At 51 gravity has taken its toll so going with a bra is not an option for me ahhh the joys of aging...LOL