Something I Never Thought I'd Admit

I'm a nurse in my 30s and recently started this open relationship thing. Last night at work, while on duty alone in the ER, I ended up with one of the patients in a supply closet. It wasn't supposed to happen like that, but there was something about him... I don't know, he had these intense eyes and a way of talking to me as if no one else mattered. We were both adults, it was consensual, but thinking back on how casual we were about the whole thing makes my stomach churn. What's wrong with me? It just feels dirty now.