I saw your post on DnJ's thread but didn't want to hijack. I'm sorry you're still in this position, but at least here you're among others who are in a similar boat
I also occasionally wonder about W and why the sudden change happened. Whether it is one thing or something else.
But then I remember it doesn't really matter what "it" is. Knowing the "why" may provide a momentary relief, but it doesn't change the result.
Logic applied to someone who is - at the very least - behaving illogically is a fruitless endeavor.
It has taken me a long time to finally start to understand this. The need to know "why" consumed me for a long time, until one day I woke up and realized how much time and energy I had spent thinking about possible present and past events and scenarios and future outcomes - and how i was no farther ahead.
That was a lot of pointless scrutiny, a lot of days and hours that I will never get back. A light bulb moment - if you will.
Thats when I realized I had to start letting go of everything, including my need to know why, my need to understand, and also my need to feel hurt at what had happened.
Granted these things are all works in progress. Some days I succeed, some days I fail. But thats sort of how life goes too.
I hope you can begin to start finding some peace within. There isn't anything you did or didn't do that could have prevented this from happening. The change isn't inside of you, it is inside of them - it is very important to remember that.