Are you eating enough?
Upping your cardio without upping your calorie range accordingly can actually have the opposite effect of what you're intending. You need to properly fuel your body. 1200 is very low, especially if you're active.
Are you doing strength training? Cardio is great, but it's actually the least important part of the weight loss trifecta... without it, you tend to lose muscle without replacing it. Building muscle makes your body leaner, fitter, and your clothes fit better even if you don't lose weight. It also help you burn more calories at rest and when you do cardio.
What do you do with your cardio (what kind, how much, intensity level), and when was the last time you changed it up? If you're doing the same stuff every day, your body can get used to it, and you can actually end up burning fewer calories than you think you are!
Sparkpeople has a great series on busting through plateaus. First part here: www.sparkpeople.com/resource/fitness_artic