Losing weight too quickly and too much?

I am 17, female, 5' 9" and a half, and 127 pounds. I think that I eat well. For instance, yesterday my breakfast was a whole wheat English muffin with honey, a half a cup of trail mix, and a banana. Lunch, a small portion of meatloaf. And, dinner, a banana, peanut er crackers, and some chicken noodle soup. I also exercise daily, with an hour long bike ride, and just walking wherever I need to go (usually at least one to two hours of walking). I would think that this would be a good way to maintain my weight, or perhaps decrease it a little, say, less than a pound a month, however I have been losing weight rapidly, almost 2 pounds a week. Is this unhealthy?