<human>: Okay, I've been charting my weight-loss over the last three weeks, and I've been losing an average of 0.5 lbs a day almost every day.  I realize that the first 2-3 weeks of weight-loss comes easily as much of it is apparently water.

Background:  I eat a balanced diet of fruits, vegetables, proteins (lean meats, usually), a couple servings of dairy a day (a glass of skim and low-fat yogurt in the morning), and I don't worry too much about watching carbohydrates.  Additionally, my portion sizes at meals are what I'd consider to be in the right range (approx. 500-800 calories each), and I periodically grab something to eat throughout the day (fruit, vegetables and the occasional granola bar.  Almost all of what I drink is water (excepting the aforementioned milk, and the occasional diet soda).

Finally, 6 days a week, I run the better part of a mile (~0.62-0.75 miles) and walk the rest.  1 day a week I fast walk 2.0 miles (pace starts at 3.2 mph and ends at 4.3 mph).

Stats:  I'm 5'10" and started at 258 lbs.  This morning's weigh-in has me at 247.4.

The last thing I was to do is lose so much weight so quickly that I get sick from it.  However, I feel fine.

Can you condense the text into a few key points?
<bot>: I'm losing weight (seemingly) rapidly despite eating the right number of calories.  Should I be worried?