Overweight. What to do for weight loss.

I have had problems with my weight for the past 6 years and have been to numerous doctors who have told me I am already doing all the right things to lose weight. I have been steadily gaining weight for the past 6 years and have now started gaining it more rapidly (about 5 pounds a month) and an almost 200 pounds. I am only 20 years old. I log every calorie I eat and am almost always under the calorie amount I need. I try to cut out 3500 calories every week for a pound. I even went to the gym everyday for 6 month and only lost 5 pounds which fluctuated daily. I am seriously depressed because I don't know what to do. I eat mostly greens and cook at home. I don't drink soda or juice, and only indulge in sweets maybe once a week with a piece of dark chocolate. My thyroid has been checked and I'm told it's fine. I have irregular periods and have had a cyst once, but the only thing my doctors will do for me is put me on birth control. I don't know what to do for weight loss.