Could you try coffee instead? I used to drink a LOT of diet soda. I recently switched to coffee, and though I add sweet cream to it, it's worth the calories in my opinion. I think it's more of a pick me up, and it does keep me full (maybe because it's warm).
IDK though. I don't really buy into the "artificial sweeteners are the devil." I switched because I prefer coffee in the morning to soda, but I still drink it in the afternoon/evenings if I feel like it.