A Double Standard Dilemma

I've been in this open relationship with Sarah for about two years now. She's great, supportive, communicative, and we both agree that monogamy just isn't right for us at the moment. But lately, I've started questioning some of my own behavior that she seems fine with, but feels wrong to me. A few weeks ago, one night after work when Sarah was out with her friends, I met a new client online who had requested a nurse who could also provide certain services beyond medical care. It's something I do on the side, not full-time, you know, just for fun and to make some extra cash. But that night felt different; she wanted me to role-play as her doctor and treat her like any other patient would be treated in a hospital setting. It was intense, but consensual. She enjoyed the feeling of powerlessness under my care, while I played the part of an authoritarian nurse, demanding compliance with strict medical procedures that veered into areas well beyond what's medically necessary. We agreed on it beforehand and she consented to everything. Yet here we are weeks later, and this nagging guilt keeps eating away at me. It doesn't seem right for Sarah to have a problem with me seeing other people while she explores her own sexuality openly, but I feel like there's something unethical about the way I pushed my client that night. What am I missing? Is it just because of the power dynamic I used in the scene that's bothering me? I've never told Sarah exactly what went on that evening, hell, she doesn't even know this part-time gig exists yet. But now every time we're together or talk about our relationship boundaries, a shadow of doubt creeps over me. Am I justified in my concerns? Do I owe her an explanation for something I did while she was away with friends? Is it better to come clean and risk hurting us both, or just keep this hidden from everyone involved?