It's much better to focus on fitness than the scale... from that you described, LetThereBeLight, you're out of shape and the allergy/breathing problems have prevented you from doing cardio. I think if you work on that, start easy, work up to more intense workouts, you'll see a positive outcome both in how you feel and how your body looks.
As for losing 20 lbs, it's possible, but something to keep in mind is that losing a lot of weight quickly by exercising intensely or really restricting your food intake... once you stop doing that, you will gain the weight back. It's far healthier to set goals you can stick to, even if that means losing weight more slowly. 1-2 lbs a week is the max you're "supposed" to aim for. It may be that lose more than that, once you start working out too, but make sure you're not setting up a standard that is unhealthy or that you will not be able to stick to long term.