[Harmony♥]

You're young. It's a simple explanation. Even if you've "always" been regular, that doesn't mean your period is going to stay on the same cycle every month. I've been regular since I had my period in the 6th grade. I've never had any issues with my period, ever. I did skip my period after I had my first one, but I learned that was normal. But, your body is probably just adjusting to a new cycle. It happens, and it's nothing to be concerned over. But, keep in mind that a dramatic weight decrease (or increase) can cause your period to get off it's cycle too. If you're still taking those water pills, I suggest doing more research on them before continuing, or discontinuing use since it's obviously not healthy that you're losing a dramatic amount of weight in a short period of time. Lot's of components have an effect on your period: stress, weight loss or gain, exercise, and even changes in diet.