Keep in mind that if you do want to burn calories, then you should employ some type of cardio into your workout. While calorie burning is not high on the list of benefits from yoga, there are many more benefits above and beyond that, as I’m sure you are noticing as you continue your practice. Keep up the yoga just as you are doing, but maybe start employing a 15 minute run each day, or every other day, or some other vigorous exercise that gets and keeps your heart rate up and your body sweating. Yoga is an awesome way to get fit, as well, though, as you begin to feel better, drink more water, eat less junk, and make healthier food choices.
Good for you, keep it up!