I was also struggling with this. I LOVE Diet Coke. To help, I just slowly weaned myself off.
Before I started the process I was drinking 5-8 cans a day! Then I went down to 3 a day, 2 a day, 1 every other day, etc.
Now, I just drink lots of Water and I stayed stocked up on all different kinds of Crystal Light packets.
I do still miss my Diet Coke but I agree with my NUT that this was also attributing to my weight. I stay motivated not going back to it by remembering how addicted I was. I was almost drinking a 12 pack a day!! Not good!
Stay strong!!!