You should be check by a Doctor, maybe you're having Tackys, which can be treated or cured. I have had this rapid heart all my life and now there is a procedure to stop them.
Hmm. While it's just a guide for exercising, a person's maximum heart rate is calculated as 220-(your age), which would make yours 200bpm. And that's not carved in stone, it's just a guide.
Is it possible that you push yourself so hard that you can get your rate up to 200 that fast? Could be. I know as recently as a decade ago (when I was 30) I would be able to pretty easily get my heart rate up into the 190's, and never thought anything of it. It was just a number to me; I didn't know I wasn't supposed to be doing that, and I felt fine the whole time.
So it's hard to give you a good answer. What's your resting heart rate, usually?