Why can't I stop eating?

I have been overweight my entire life. I have tried several diets - Jenny Craig, Weight Watchers, slimfast, nutrasystem, Atkins, I've gone to doctors and even went to fat camp as a child. Nothing works. I can't stop eating. I refuse to have byp surgery, but I need to lose weight. I am 30, 5'5 and 270lbs. What should I do?