I've heard breasts actually don't stop growing till you're in your early 20's, there is yet still hope for you.
Anyways, to be honest breast size isn't nearly as important as proportion. As emily said, most slim girls tend to have smaller breast size, which is fine if it compliments the proportion of your body.
Plus if a guy likes you enough, he's not going to give a shit about how big or small your boobs are. You just have to know how to work it. Don't fake it though, that'll tick a guy off. So stop with the padding and shit, that's the only thing that will disappoint is a guy seeing big boobs and not getting it when the bra comes off. So don't fake it, let your confidence show through.
If it will help, here are some photos of some beautiful women with a flat chest.
In conclusion dollface, you're beautiful so long as you know how to use what you have to your advantage. I'm aware there are tricks like push up bras and stuff you can use to make it look bigger, but it's really not that big of a deal. Confidence is way more sexier than some fake tits.