I have met a young man with a similar body to yours, and while I don't remember the name of his condition, he decided to have it treated with hormone therapy and had great success....but that doesn't mean it's for you, or necessary by any means!
As for your other question, my own breasts, each of my three sisters', and most of my gal friends' stopped growing by 17-19 years old. But as schnookiepie said, the size fluctuates with weight gain or hormone changes. Every month I go from an A-cup to a large B-cup just before my period...