Wife's Secret Playground

I thought I knew my wife inside and out, but last week turned everything upside down. We were at a party where everyone was dressed up in costumes, and she took me aside to tell me she'd been experimenting with strangers while we were married. She said it was just roleplay and that she loved me too much to cheat for real. But the thought of her pretending to be someone else with another person...it's eating at me. I feel so stupid for not seeing it coming, but also grateful that there wasn't anything serious happening behind my back. It’s a new world between us now.