Unintentional Weight Loss

I'm 24, 5'3" and have weighed 107-110 pounds for as long as I can remember.   For the past month to two,  I've been losing weight.  I recently weighed myself, and weigh 90lbs...   Friends say that it's not noticeable, and seem to shrug it off.   I'm not intentionally losing weight,  and I don't want to.   I have had a bit of a loss of appetite, but still eat lots.