Answer: You may be at a plateau, which eventually happens to everyone. As you get in shape, you become more efficient at burning calories (like getting a tune-up for your car) which means that you burn fewer calories than you used to. If you tend to do the same thing for your cardio workouts, consider changing it up (Stairmaster one day, bike the next, jog the next, or try the elliptical or rowing machine).
You’ve probably had to reduce your food intake and increase your activity level a lot during the time you’ve been losing weight. If you choose to continue to lose fat, make sure you have room to add activity and/or lower calories and still enjoy what you are doing. If not, stay where you are for now until you feel like taking another run at losing weight.
You must be able to maintain the lifestyle that got you to your current level of fitness. If it is too hard to maintain, you won’t. You may be where you need to be from a health standpoint.