The best advice I can give is to make small changes. They do add up. You have this problem due to constant excess. Fixing the problem isn't going to be fixed by another extreme.
It's easy to say and the most difficult thing for a human being to do; lifestyle changes.
Because it's overwhelming when you try to accomplish drastic changes, the best way to change behavior is to slowly modify your habits until they become routine.
Also, I know a lot of people are mentioning exercise. Diet is 80-90% - You can exercise like a madman, but unless you get control of such a big part, nothing will happen; in the long term.
Exercise is by all means important, but the only thing you should really be doing is moving more until you take yourself down. 1-2 pounds a week is safe and will allow the skin to bounce back more smoothly. Insert more exercise as you go.
That said, if you are truly addicted, you may need assistance from a psychologist. If you think you can buckle down, you could also hire a dietitian to help you learn how to eat healthy. They can plan out meals, etc.
One of the reasons people fall off healthy eating is that they have had such rotten food, they crave it. Once you get that "poison" out of you, you'll find that certain things in excess will actually make you ill and will cause you to lose appetite.
I stopped drinking soda and now I can't stand how sweet it is. That changes for everyone, though.
Lastly, while your stomach is decreasing in size, eat very small portions every couple of hours. You can also put fiber in water and keep up with lean meats, for protein.
This does two things:
1) Helps you curb cravings.
2) Keeps your metabolism burning, which burns fat.
If you do not keep up a good intake of protein and you do nothing to supplement the building of muscle, you will lose both fat and muscle. You want muscle to keep your furnace burning, brightly.
PS Plenty of good advice here. I wish you the best of luck.
PPS I once weighed 310 pounds (5'11") - I'm now at 160 and very well toned. This took from age 26 to age 28 to accomplish.