I've had the same problem. I found the Victoria's Secret miraculous push-up halter top to do wonders. It's heavily padded - but in the right places. I know it's "cheating" but I don't care; it makes me feel sexy strutting down the beach.
babe, just love yourself ! i've been 34A all my life (23 yrz old now) and "sometimes" i change for B (that is when they sell small cups) but SO WHAT ?! i know and BELIEVE i look great ! i have a pretty face, i have nice thighs n hips, nice slim waste and i just look adorable :D and i'm sure u even look more beautiful than i do, dear, just believe in you, believe in yourself, love yourself as God has created you, walk with your head high and have a big smile on your face, don't let anyone whoever is to let you down :D and please i recommend you to check some actresses they just look hot even though they have small breasts, like keira knightly who would dare say she is not sexy ? no one wud she's just wow, also charlize theron (spelling not sure) and the list goes on, those women just look fantastic in evry single way and they don't give a damn about their breasts size :) just believe in yourself, love youself the way you are, appreciate what God has given you and ur all okay :)