My Self-Centered Ex

Why in the heck was my ex so self centered? Did our actual life HAVE to revolve around him? What ever happened to "us" meaning"we" ," him and I" and not just him? Do we get in a relationship and get so comfortable that we start losing our spouse over the petty things in life? I was a very good spouse......cooked, cleaned the house, did the laundry and yes, he had as much sex as he wanted, so what went wrong? Did I forget to make his food the way that he liked it? Or was his clothes not done right? Oh, or maybe the kids were making too much noise? We did have a communication problem at times because he just didn't want to know when the bills were due, he didn't want to hear any of the kids school things, he just didn't want to be bothered, and so I took care of it all. Oh, maybe he just felt like the only thing he had to do in our relationship was to work and I was to do EVERYTHING else. Did he have to be so into himself that he just thought in his own mind that I would never find out about the OW? I didn't owe him the luxury of having another woman. I thought that marriage was about 2 people, not just one. And what does forever mean? In my case, it only meant 13 years.