that fat laden calorie

I've never been a calorie counter. too hard. I just relied on exercise and more exercise to keep the weight at semi bay. but working from home and my new uber sedentary lifestyle has meant drastic measures. yesterday, I did a double exercise class again and still I only burnt 1900 calories. how is that possible? my bum is burning from all the squats today. I only burnt 150 calories more than I ate and trust me, I ate so little for me: rice krispies plus blueberries. some sushi and an average portion of taco rice (OK, not so good for me, I admit). no fun drinks in sight. given that you need to have a net loss of 3500 calories to burn 1 one pound and I'm pretty knackered from all the exercising, this just sucks, at the moment.