Hi Gazeboigirl,
It's actually a myth that muscle weighs more than fat. Fat and muscle weighs the same, but fat takes up more space (volume) due to its composition than fat. Musle is heavier by volume than fat, but 10 pounds of fat and 10 pounds of muscle are the same. That's why with more muscle, you'll look tighter and smaller.
I know you said you don't want to build muscle, but building lean muscle mass is actually the best way to aid in your overall weight (and fat) loss and keep it off. The more muscle a person has, the more metabolically active they are, burning calories and fat, even at rest.
Adding strength training to your progam will help a great deal. It will help you burn calories at a faster rate and promote the production of new lean muscle mass. I recommend you begin a program for your total body, twice per week. Follow the recommended strength training exercises on this site under "mystrengthtraininglog" for some great upper body exercises as well as demos. You are trying to target your shoulders, triceps and biceps primarily, and the exercises on the site are all great basics that will help you reach your goal.
Continue this with at least three days per week of cardio exercise, 30-60 minutes each, and you will start to see results.
Good Luck,
Paul