Training My Way To Taboo Comforts

I've been a personal trainer for about five years now. I'm thirty-two and my partner, let's call her Sarah, is an editor at a local magazine. We've been together for three years, and we love each other deeply, but there's something that makes me feel like we're drifting apart lately. It started with small things, like when she couldn't understand why I needed to touch people in intimate ways while training them. One day, one of my clients, a woman named Clara who was in her twenties, showed interest in more than just fitness. She's always been attractive and we'd developed a playful dynamic over our sessions. She mentioned during one workout that she liked the way I made her feel and asked if I would be interested in something outside the gym. Surprised by her boldness, I told her I wasn't sure since I'm in a committed relationship. But then Clara began to hint at specific kinks I'd never thought about before. She talked about the feeling of control when someone else sets limits for you, but it was more than just roleplay; she wanted me to take on an adult caregiver-like figure who enforces rules and boundaries over her. It made me feel strange, both intrigued and guilty. Over time, I found myself thinking more often about Clara's proposition. The thought of being in a dominant position felt oddly satisfying. But then came the guilt again. Sarah trusts me completely, and I could never betray that trust with another person. Or could I? A few weeks later, I made an excuse to leave a party early where Sarah and some friends were enjoying themselves without me. As I walked home alone in the dark, my mind kept wandering back to Clara's words. I even found myself dialing her number once or twice before hanging up quickly. I'm here because I need guidance. Am I being unreasonable by wanting this kind of experience, even if it's consensual and just a fantasy? Can someone still be faithful while exploring their darkest desires in private with another person without hurting those they love? It's like trying to maintain balance on a tightrope between the joy of living my life fully and the fear of falling into places I don't want to end up. Clara mentioned she has friends who share this interest, but that doesn't make it less confusing for me. Any thoughts? Comments or advice are welcome.