I think you need to take really small steps and build habits that you can sustain. Don't focus on weight. In fact, perhaps it's best not to step on the scale for a while.
I do get fizzy water, but that 0 kcal, lemon flavored stuff. It's quite nice, but it's really just flavored water with fizz. It's not soda, so no sugar whatsoever. It's also not sweet at all, so it takes some getting used to. Apart from that I drink water, coffee and tea.
You could try walking in really short sessions every day. Start with like 5 minutes. That keeps the threshold really low, but it builds the habit of walking. Once it is a habit you hardly need to think about and it doesn't feel so hard, extend your walks by 5 minutes at the time. You could deliberately limit yourself in the beginning, so you'll look forward till you can walk again. You make it a forbidden fruit, so to speak.
You can also try planking. Start with just 2 seconds 3 times in a row. Build it up really slowly. Here you weight could actually be an asset, as you are using it to build muscle, which is really important. If you can't do a full plank, you can start on your knees or against the kitchen counter.
Food wise, I try to keep all sugary and UPF stuff out of my house. This means I don't have anything I can just grab to eat, with the exception of fruit, nuts and the boiled eggs I always keep ready in the fridge. If I want to eat something more substantial, I have to prepare it first. I batch cook on the weekends. This habit took me a long time to build, but I saves a ton of money (which I can spend on things I actually like) and my meals are far more nutritious. Don't worry if this habits slips from time to time. Don't beat yourself up over it and even get yourself a small treat once a week, that you know is not good for you. It can't hurt if it's only once a week and it helps to reduce food obsession.