Genetics plays a large role in breast size, as well as diet and how much you weigh. If you're small framed and you don't weigh much, you're likely to have smaller breasts. You could also be a late bloomer and may get your breasts later on. Women tend to develop into their early twenties, whereas men have long since finished.
I'm 21 years old and a proud A cup. I used to cry and I used to hate myself for not being born with large breasts, only to discover that my large breasted friends (DDD cups) envied me for how small and perky mine were. Smaller nipples are also more sensitive than larger ones, which is something I was told by my doctor. A lot of my larger breasted friends struggle with stretch marks, clothing issues, stares, back pains, awkward sex, and overall not enjoying how their breasts look when they aren't being pushed up by a bra.
I thought that I would be rejected for girls with larger breasts when it came to dating, but I actually garner more attention than I can often stand.
Both my mom and her sister got breast implants when they were younger, being small breasted themselves. My mom recently had hers taken out, because she hated them and felt cartoonish. They also messed up years ago and damaged a nerve in one n****e, so that one n****e is always hard while the other is soft. She says that she regrets ever getting them, because she was very much in pain after the operation and when they healed, she felt fake.
I realize that it's easier said than done and of course, implants are always your choice should you decide to go through with that in the future. However, the grass is not always greener on the other side.
I really hope that this helps you.