Is it possible to have...alternative eating habits, though not because you think you're fat, and still have an eating disorder?

For the last few months of school I dropped my calorie limit a lot (are you allowed to say how much? i know you can't mention body measurements), and lost quite a bit of weight, more than I was expecting. But I didn't start because I think I'm fat, because I don't, nor do I think fat is bad. I just...wanted to make things harder on myself. I'm at home for the summer and am eating (mostly) normally (I try to keep the food intake down but am eating more than I did at school), and I'm dealing with it fine. I fully intend to drop my calorie limit again when I go back to school, though.

Could this possibly be an eating disorder (or the development of one), or is it simply personal choice?