Hi, diet soft drink addictions can be really hard to overcome. My vices were Coke Zero and diet tonic water. I tried to cut it out but always gave in after a day or two. What got me off it was a 7 week holiday where I just didn’t have access to a constant supply and as I was travelling a lot, I was grateful at times to be able to fill my water bottle from taps in public rest rooms. Something I never thought I’d be able to do.
Now I’ve learned to love water, and may allow myself a fizzy drink once every couple of weeks. I’m careful not to fall back into old habits. Sorry that you’re going to have to tough it out the hard way, but it can be done. I really enjoy my water now.
Good luck, this is the first diet I’ve been able to stick to for any length of time, and it does work even if you can’t do the exercise part. Just follow the diet and do what you can.