Don't go on the pill and fill yourself with chemicals unncessarily. So what if you are flat chested, that just makes you one of two things, the same as a lot of people or individual and different. If you meet a guy and his line is 'do you come here often, and what cup size are you' then you'll probably not be interested in him anyway! Chemicals and surgery are really bad options compared to being natural. Look at the surveys out there. Most men, regardless of what you might think, prefer natural, small chests rather than the hideous big flabby fake ones.
And when you are 50 and those around you are scooping their boobs up so they don't bash their knees, you'll be still standing proud.
You may or may not develope more, but be happy. I saw a programme the other day with Kate Lawla talking about her small boobs and she was way happy. Saves money on bras too. What's sexier, a slingshots that get on your bloody nerves or being free under a Tshirt - if you know what I mean