It sounds like you and your BW are still together then? Are things getting any better?
Stupid people do make stupid mistakes, but infidelity is usually a bit deeper than just being stupid. You do have to think about yourself in that regard. You have to spend some time on your own stuff to figure things out, to figure out why you didn't talk to her, to figure out why it took you 28 years to figure out that communication is key. Why did it take so long?