Kuan,
Happy birthday. But forget about the formula! I have read that it is not very accurate for most people. For me, the simple 220-age formula says my max should be in the 180s. However, I have done two max hr tests myself, and hit 200 both times. I often hit 193-195 while doing intense speed work (running) at the track.
There are several ways to find out your max. Try to look up more info on the Internet, or if you can, pick up a good book on heart rate training. I run more than bike, so I am partial to a book by John Parker called "Heart Rate Training for the Compleat Idiot." Parker is a runner, and it is geared more toward the runner. But I'm sure there are good ones out there for cyclists too. Maybe something by Joe Friel?
Good luck.