Why do you care if your breasts are that prominent? I'm the same size as you, bra-wise (slightly shorter), and people will think you're certain ages on a myriad of criteria. The ones who count will judge your age by how you carry yourself. If you slouch and look all teenage sullen, you will look younger. If you stand up and act with grace and confidence, you will be seen as mature, as long as your language further proves that.
It sucks people think you're younger than you are (I think I could conceivably pass as middle school age if I dressed and acted a certain way), but boobs aren't the end all, be all of age indication. Most people use height to figure out age or sometimes roundness of cheeks, etc. Very rarely do I hear of anyone considering breast size as an indicator of one's age
From your photo, you're not Pam Anderon but it's obviously you aren't flat either.