We all go through the boredom and lack of motivation to continue this journey. You're doing great by still finding time to make your lunch break productive. Walking the stairs is some of the best exercise. Try to increase the stairs to five times.
You have a great DVD collection, either wake up in the morning after a few weeks it will be habit or pop in a DVD as soon as you get home. Rotate your DVDs to eliminate boredom. After 30 days of consistenly working out then reward yourself with a new DVD.