Not dying early of a heart attack is a pretty good motivator for me. : ) I've been border line bulimic in the past, and let me tell you, it's not fun, it's not glamorous, it's not sexy and it doesnt make you lose weight. If you decide you have to have a hamburger, do it! (Don't do it all the time, but once in awhile won't kill you). Don't throw it up. And if you're worried about feeling bad afterwards, take the gusto to tell yourself NO! I DON'T NEED A HAMBURGER! in the first place! All eating disorders do is make you obsessed with something unhealthy that will eventually kill you. It's not worth it.
Even if you can't stop the junk food, just remember: smaller portions. Even that will make a big difference. But if you can, cut back on calories (sugar is the silent cuplrit that will make you fat!) and be more active.
Even if it takes awhile to lose the weight, at least you'll be alive and healthy to enjoy your new body.
Good luck.