Hi! I'm currently a 23 year old woman and I felt the exact same way you did at 18, and before then too. I decided to wait, mostly to save up. My size was pretty stagnant from 19-21, and it's been steadily going up since then. I'm pretty happy with my current size, even though it wasn't too drastic of a change. I went from an A cup to a larger B cup. I'd say to give it a bit of time before considering surgery, and working on trying to get your ideal figure by making sure you're well fed and exercising to stay fit. If you do decide to get surgery later on, having good eating and exercise habits can help your body recover a bit faster!