The health risks of artificial sweeteners and caffeine aside I'm not sure you have an addiction. Just because you enjoy someting and partake of it regularly IN MODERATION (capitalized for emphasis) does not mean you are addicted. A true addiction controls your thoughts and actions. It interferes with your life and happiness. It is a burning desire to obtain whatever it is over all other activities.

My husband truely likes steak. He orders them when we go out to restaurants. I make one for him almost weekly. He greatly enjoys the meal but he is not addicted. There is a difference.