Do you count calories, restrict what you eat, fast? Overexercise? Rapid weight loss usually does mean things are not right, and if you don't have an obvious physical reason, it could be an eating disorder. Were you underweight, normal weight, overweight to start with (honestly, which one because everyone with an ED thinks they are overweight even when they are not, but going by height/weight/gender charts, something like that)? What about now? Do you worry about gaining weight? Do you keep setting goals to weigh less? Do you weigh yourself all the time? Have you stopped eating foods you enjoy? Do you throw up or exercise to compensate for what you do eat? There is a long list of ED symptoms, too exhaustive to list here.

The only one good reason I can think of for normal rapid weight loss in an individual who is not overweight would probably be having a baby and/or nursing (couldn't keep weight on while breastfeeding). I got to my pre-pregnancy weight in under a month (gaining the normal 25 lb. the OB expected while pregnant). Other reasons are not so good. I had a rapid weight loss this year, but it came from a perforated duodenal ulcer (unrelated to the ED), and the hospital treatment for that is brutal; just google it. I lost over 10 lb. in 6 days, and then post-surgery, foods taste weird, you're not hungry, you hurt horribly. In that case, it was a medical issue (one that could have killed me, so I was lucky, I guess).

If others are concerned, you should probably get checked out. If you have no ED behaviors, it could be hormonal, something like that. But if you DO suspect you might have an ED, it is best to get into treatment as soon as you can. The longer you wait, the harder it gets.