You might be out-eating your cardio. Do not think that just because you are working out a lot you can eat a lot too - no. Losing weight is burning off more calories than you eat. If you burn off 800 and eat a 1000 - you'll gain 200. No matter how hard you are working out, you can always make this mistake. Just a friendly heads-up!
By the way - If you think that just because you eat very well cardio is not important, it still is. Cardio is one of the most important things you can do to improve your body. Ofcourse, you can lose weight with just nutrition. However, the two combined will grant you a healthy body!
How long will you have to keep this up? Here.