I don't have enough information from what you posted, but a few years back, one of my best friends was in the same situation. He was eating and eating non stop and instead of gaining weight he lost weight. I believe he went from around 155lbs to 125lbs in a little over a year. After getting checked out, they found he had developed diabetes. If you continue to lose weight and you don't feel right about your weight, I'd recommend getting checked at your local doctor. Again, I don't have all the information, but it sounds eerily similar to what happened to my friend.