Fucked is definitely what it is.
I know of someone here in the same boat. Actually I hear about it all the time. It ends in desperation and then cheating almost always.
The illusion that getting married, having babies, going into debt is what will bring a relationship some strength and togetherness is absurd and stupid. I get so frustrated with the laziness of some people and then the expectation that I am in some way am suppose to feel bad for them. There were signs, they didn't observe them. There were decisions made out of being too afraid to say "no, this isn't working." Yet the person blew them off and chose to ignire them because it was easier.
My frustration comes from all the hard work I have done in my own relationships and that I am expected to just let cheating pass and be sympathetic. It makes me just want to tell people to fuck off actually. I have little patience...
at least today. Sorry, its not helpful to you.