Aware that my stories are usually TOO long, thought I'd take a stab at a 750-word effort
Kelly and I married in our late 20s and decided on no children, turns out it was a good choice after seven years. I had a feeling that something was wrong. Investigation followed with the typical cameras and mics hidden throughout the house and her car. Easy for a professional techie like me.
I discovered that Kelly was cheating whenever I left on business. My trips usually lasted a few days but could longer. I didn't know, and had never seen, her paramour. I learned that he was a former boyfriend named Mike, now himself married, necessitating meeting at our home. I guess he faked business trips so he could fuck my wife.
Our sex life was pretty good, nothing crazy, but the stuff Kelly did with Mike was downright kinky, stuff she never did with me. I never knew Kelly had such a submissive side and was shocked at her enjoyment of many degrading acts.
We had a strict prenup since we'd both been cheated on before. In fact, I think Mike was the boyfriend that cheated on Kelly before we met. In the prenup, I kept my business (as I started it before we met), and Kelly kept a small family trust fund that was worth a fraction of my business. Any infidelity resulted in painful financial penalties to the cheating spouse. Especially harsh for Kelly since she chose not to work.