On this topic, I totally sympathise with you. I too have gone from 70 to 95 and back to somewhere in between. Strangely, I have been active this whole time, running 5k to 10k most days. It must be the food I eat and otherwise pretty sedentary lifestyle.
You know what they say, you can't outrun a bad diet. Clearly that is the truth for me.
Still, I have committed myself to running a marathon, and I think the journey is most definitely worth more than the end result. You said that you are going to start walking and tracking your steps and calories. That's how I started too, and it became strangely addictive. I believe you have the character to turn this around 180 and probably make yourself the best shape of your life!
Yeah let's see how it goes with the walking for the first week, will try to improve on it every week.