If you're having trouble losing weight through exercise, I would consider severe calorie restriction. Your best bet is to drop your calories down to around 1000 or less for the first few days, and gradually bring your intake up to around 1200 (the initial lower amount is to shrink your stomach and get some "instant" results; water weight, but still psychologically motivating).
Generally, it is far easier to stick with calorie restriction than exercise, especially when you are overweight. You'll notice the improvement (on the scale) more easily, and be able to focus on your weight as a motivating factor. Once you get down to a bmi of 24 or so, then you can slowly increase your calorie intake (focusing on healthy foods). Once you're back up to a reasonable amount of calories, you can begin working out.