A Complicated Decision I Made Tonight

I've been engaged to a wonderful man for over a year now. We have so much in common and are deeply committed to each other's happiness, but lately, something has been weighing heavily on my mind. It started when I met Sarah at a trans support group last month. She’s someone who understands the complexities of being trans that others might not fully grasp. We clicked immediately, and over text messages, calls, and brief coffee dates, we grew closer than I ever thought possible. The connection was intense, both emotionally and sexually. Last night, we made plans to meet tonight at a local hotel under an alias, something just the two of us without anyone else's judgment. The moment our lips touched, it felt like everything that had been building up inside me erupted. There was no more holding back. We undressed each other slowly, exploring every inch of skin as if it were the first time. His hands moved with such tenderness over my body, tracing curves and hollows I never thought could feel so good. As we lay there together, his fingers slid inside me, finding that spot that made all coherent thought scatter into nothingness. We both wanted more; he pulled out a condom and sheathed himself carefully before entering me fully. The sensation was unlike anything I've ever experienced, it was raw, passionate, and utterly consuming. In the aftermath of our lovemaking, we stayed entwined for hours, talking about everything and nothing at once. There's no denying how much I care for both my fiancé and Sarah now, but there’s also this nagging feeling that what happened tonight might be something I can’t go back from. I feel torn between the love I have for my fiancé and the undeniable physical and emotional connection with Sarah. How do I reconcile these feelings? Am I an asshole for even considering pursuing a relationship with someone other than my partner, no matter how much we both seem to want it? Your thoughts would mean so much to me right now.