Exercise intake balance

I recently upped my exercise to 40 minutes on the elliptical 5 times per week, followed by 20 minutes of light weights, as well as walking 30 minutes of brisk walking throughout the day while at work. The problem is I am so exhausted that I fall asleep at my desk. I upped my intake to about 1000 calories per day and my weight teeter totters btwn 2 lbs. I feel like I am going nowhere fast. What are some of your exercise regimens and what does you r intake look like?