Today was my third CO2 laser treatment sitting, but I have noticed that there is less redness and burning

The laser is designed to attack the color of your hair at the follicle. The instant surge of high heat kills the follicle. As the quantity of hair diminishes, so to does the discomfort. There's simply less follicles absorbing the heat. 
Bottom line; you're demonstrating good results and your provider isn't playing games.
Be sure to stay on schedule with your treatments. Hair grows in cycles. Approximately 1/3 is active, 1/3 is dormant, and 1/3 is either going active or going dormant. A follicle can only be killed when active. 
Thus the reason for multiple treatments. Get off the cycle (a treatment about every 5-7 weeks - every 6 weeks is considered ideal) and you may as well start a whole new set of cycles or be doomed to untold number of touch up treatments. The provider will love all the extra visits, but it won't help your wallet or busy schedule.
Sometimes we can get all the hair in 4 treatments, much of the time it requires 6 treatments.
Wishing you all the best.
Warmly,
Arbella Sarkis, MD