Girls, do you ever have trouble finding a dress that fits right..around the breast area?

ok..so, first of..im a girl, 16, and i have DD's. i can NEVER find a dress that fits right, around my boob area. like you know how most dresses have like a bra in them, to hold up your boobs so you dont have to wear a bra..well, every single dress i try on..its not big enough up top. i try larger sizes & its still the same..its not just dresses either, i have a singlet that fits great but it has a built in bra..and that doesn't even cover half my boobs -_- my cousin has E's..and she can NEVER find anything that fits her, she wear oversized t-shirts most of the time.. my aunt has FF, (they are real lol..i come from a family of big boobs) and she can hardly ever find anything.. is it just Australia? or something? do they not make clothes for girl with bigger boobs? anyone have this problem?