Hi N.. First major kudos and congrats to you for losing whatever you have up to now, and making your health and fitness a priority! Take a moment to recognize and appreciate that for yourself.
Now, let's get down to the business of those last stubborn-mama 15 lbs, that so many of us experience. Know that you are not alone in your struggle, but it CAN be done! I don't know exactly what kind of exercise or diet you are currently doing, so I'm sorry if what I say is repetitive....
The best way to lose weight and be healthy is to eat "clean". Go to http://www.ehow.com/how_###-###-####_eat-clean.html for a great summary of what that means and how to do it. Oxygen magazine often has great eat clean recipes, and Tosca Reno has written several cookbooks for recipe ideas. Once you start to eat clean you will not want to go back. You just feel great! I've been consistently doing it for about two years now and cringe at the thought of eating the way I used to.
As for exercise, the best way to lose weight and stay fit is to combine weight/resistance training with cardio. Depending on how many days a week you have to workout, make a plan and stick to it. For example, if you can exercise four days a week, lift two and do cardio two. The most important thing is to constantly vary your workouts, don't keep doing the same things over and over and expect a different result (some say that is the definition of insanity). One day lift heavy but fewer reps, one day do interval cardio getting your heart rate up to it's max for 30 seconds, and then resting for 1 minute (jump rope, sprint, stairclimber, etc will all work for that). Repeat that cycle for 15 minutes or so, or more if you can. One day do lower weight with higher reps. One day do steady cardio for 30 minutes. One day do circuit training - a couple of resistance exercises, then do 1 minute of a fast, hard cardio burst to get your heart rate up, then go to a couple more resistance exercises, then repeat until you've worked out for 30-45 minutes.
Some good websites for exercise ideas are fitnessmagazine.com, bodybuilding.com (it's not all huge bulky bodybuilder stuff, I promise!),and eatcleandiet.com. And Oxygen magazine is the best fitness publication out there for women. And google, google, google. You can find great workouts and articles online.
There is no pill that can do this for you. It has to be done the old fashioned way, I'm sorry to say. If you are trying to lose the last 15 you have to REALLY push yourself in the gym and really be meticulous about what you are eating. It will happen, I promise!
Good luck to you!!!! You can do it girl!!