Brain damage? No, seriously, I hit my head hard when I was young and have a seriously defective sense of smell. An accident of this sort can lead to all sorts of problems. Then there's the possibility of a genetic defect. Quite a range of things to choose from, but you should try to control your weight for health and social reasons.
Why are you eating weight gain tablets - I would have thought appetite control measures would be more logical.
You could be a compulsive eater?Its an eating disorder. Its more common than people think, if you feel like u have a problem tell someone. But dont feel like your weird or anything, everyone is different.