Or... you had an eating disorder... you weren't eating much.  Of course you're going to drop weight in an unhealthy way... you may have been putting too much strain on your body.

But now, you're eating a proper diet and exercising the RIGHT amount for your body and the diet you have.  Doesn't it make sense that your body may be going through some healthier changes now?

Give it some time, You may start gaining some weight back, but it will most likely be more in muscle from exercise and the like :).