Why do they get to be happy while I have to live in pain?

My ex cheated on me for over a year with a coworker of both of us, he knew all about me and was happy and willing to continue this, all while acting like nothing was wrong to my face. When I confronted him after I found out, I did not get an apology or any sympathy whatsoever, rather he told me to grow up. 2 months later I have to still work there with both of them as I can't financially afford to change job. They are both dating new people (also at work which I have to see everyday), everyone is still friends with them, they are still friends with each other. I always see them happy and they don't seem to have suffered any consequences while I live in horrible pain every day

Why isn't life fair?