A Secret Shame

I've been married for nearly two decades now and I thought we had a good relationship. But there's this one thing that happened last year when we went to a swingers' party out of curiosity. It started as just watching others, but then my wife suggested I try it with someone else while she looked on, just once. She said it would be an adventure for us both and help spice up our sex life. We agreed on rules: no real names or contact info exchanged and no one-night stands afterward. In the heat of the moment, I ended up actually enjoying it more than I expected to. It felt so liberating and intense that I came back for a few more encounters with other couples throughout the year, always keeping it anonymous and just for fun. I'm terrified she'll find out though.