I have a secret! I was my co-worker's mistress, I loved it.
Wow, that sounds unusual. Tell me about your relationship.
I've dated him since long ago when I was in high school, but I knew that if our relationship went public it would endanger my friends' relationships, I felt bad about it.
I see you feel bad about it, but you shouldn't have been having a relationship with him in the first place. If the relationship does go public, you risk losing your friends' relationships as well as your reputation at work.
I'm not afraid of losing my friends and I think my own reputation is not that good.
You should be concerned about destroying your friends' relationships. It is a huge betrayal to them and to yourself to have an affair like this. You should have more self-respect; even if you think you have a bad reputation you should still try to do the right thing.