D.K.
Caffeine is addicting. However one diet soda a day I don't think is bad at all. Granted, coffee, tea is a much healthier way to get your fix.
I started every day off with a diet mountain dew, didn't care for coffee. Then last winter I got bronchitis and I had some coffee with yummy flavored low fat creamer in it and I was hooked, just one cup every morning but I have that instead of the mountain dew. Then I went to Green tea, it has caffiene but not nearly as much but has natural energy boosters, it was a gradual unintentional change.
I don't think you are "addicted" having one, I don't.
I actually was allowed one diet soda a day while pregnant because the first withdrawl symptom was migraines and I already suffered from those and they OB didn't want me to have the kick up, just one, that was all I was allowed.
Chocolate has caffiene in it, minimal but it does.
Addiction is when it overtakes your life and you cannot live a day without it thinking that is the only thing allowing you to function well. Five a day, that maybe be bad and excessive. Research now shows the anti oxidants in tea are wonderful and there are healthy aspects of coffee too, if not drank in excess. Nothing wrong with a cup a day.
Just see if you can go one day, alternative like tea, where you get a little caffiene but not much. The sugar in real sodas and the artificial sweetners in the diet are what is horrible for you! Not the caffiene. Caffiene in moderation is fine. One can of soda has like six tablespoons of sugar, the carbonation is terrible on your teeth, the artificial sweetners trick your body into craving sugar. So that is why sodas are bad for you.