Hey, I am in the same boat you are. If you are really desperate to lose weight, try the diet that I posted under "a diet curing all?????" on the open to all topics board. It's pretty drastic, and I felt very sick from it for the first few days, but now I am getting more used to it, and I have lost about 9 or 10 pounds in a little over 10 days. it is a zero carb diet, and is much more strict than atkins. The most you should do the zero carbs for is 2 weeks, and then slowly start adding some back. I did zero carbs for about a week (hated every minute of it, felt sick ALL the time). Then my dr added some rice to the diet. Any kind I want, as much as I want, as long as I don't overdo it. I must say that I do feel much much better now that I am eating the rice, but I probably would not have lost weight had I been eating it from the beginning. if you cannot tolerate doing the no carbs, then have some rice. This diet is merely a suggestion.
This diet is very very radical and is certainly not for everybody. You should definitely discuss it with your dr before you decide to do that, or anything else including exercise.
If you are really want to do some exercises to flatten your stomach, get an ab-roller! They are the best! Other than, all I can say is, cardio, cardio, cardio. Walk, run, swim, jump rope, etc... But always be sure to ack your dr before you start any new diet or exercise program. And if you join a gym, they can show you how to use the equipment (treadmill, weights, ab roller, etc...) properly.