I agree with the posts above
....a doctor or nutrtionist can be a big help. Other fairly simple options are healthy weight loss plans like Weight Watchers, Jenny Craig or simply counting calories. The organized plans are easier (if you need to learn about how to make good choices of what to eat) - but obviously they aren't free. I personally count calories, the best advice I can give about that is you want to make sure you don't go below 1200 calories a day. Losing the weight slowly is better for you and will give you a better chance of being able to keep it off.
Last but absolutley not least, exercise,exercise, exercise.
It's good for you physically as well as mentally. Start slow and build up a little more time or intensity each day. Crank up the mp3 player and take a nice walk...
Keep in mind that you deserve to be healthy - and you are beautiful no matter what size you are.