S.W.
Get your levels checked by your doctor. If they come back good, then it's most likely what you're eating. Extra calories can sneak in when you least expect it, ESPECIALLY non-diet beverages and food you eat in restaurants (restaurants are BAD for adding extra fat from things like butter and cream to add flavor). My suggestion is to record the calories from what you eat for a week. If you are eating more calories than 10 times your weight, that's why you're gaining weight. To lose weight, you should be eating calories that total less than 10 times your weight daily (but no less that 1200 calories a day because that's not safe). For example... let's say you weigh 180 pounds. If you're eating 1800 or more calories a day and not exercising, that's why you're gaining. If you're eating less than 1800 with or without exercise, you're guaranteed to lose weight (as long as your thyroid levels are normal).