Workout with bad back

Hi all. I have recently upped my workout to 2x a day because my weight loss has been very slow lately. I was in a car accident in 2001 which left me with some back problems. This limits my exercise options.

Currently, I am going to the gym in the morning and riding a stationary bike for 5 miles and at night I walk the indoor track 4-5 miles while my daughter is at practice. I average about 13 mph on the bike and 16-17 minute miles.

My calorie intake is between 800-1100 (usually right around 900) and Protein, Water and everything else is on target) According to the calculations I have, I should be burning 230 calories on the bike and between 280-300 walking.

My question is with an average burn of around 500 just with my workouts, how the hell is the scale not budging? Do I need to change my intake?