i ve been gaining a lot of weight really fast so that now i have stretch marks, no i m not pregnant, never married or had intercourse. i m 20 years old (female) and have always had a really high metabolism and have never really gained any weight. i m always tired, always have a headache, always feel nauseous. i drink plenty of water and exercise and eat a really healthy balanced diet but can t seem to get rid of the weight. also i have really bad menstrual cramps, am often irritated or very sad, and cry often. HELP!