W has always been a little vague about what our problems really are, and even my role in them. What I've been able to glean is that ... Well, actually, rereading that, it's kind of a lot.
That could seem like a lot... but you have to also list the good qualities you've manifested all these years to have a balanced view. I'm sure you've also done many things right during those times. And it's on *both* of you -- not just you alone -- that her feelings have somehow drifted to where they are. Both of you should have taken care of your marriage actively so your feelings don't drift that far from a healthy place.
Everything I say above applies to me too. It takes two to tango.
Me: 50, MLC/WW 45 Young kids Nov 2015: BD1 Apr 2016: BD2 Jan 2017: W filed Feb 2017: D final