Caught in the Act: A Professor's Dilemma

I'm a fifty-something university professor who has recently become engaged to my longtime girlfriend. We've been together for five years and she's everything I ever wanted in a partner, intelligent, kind-hearted, and our relationship is solid. However, things took an unexpected turn last week when I decided to explore a side of myself that I never thought possible: I was intrigued by the idea of swinging with another couple we know well from campus. I confided this interest in my girlfriend during one of our many deep conversations about life and love. She wasn't entirely against it but felt nervous about how it would affect us if we didn't both feel comfortable enough to move forward together. We agreed that exploring separately, while still committed to each other emotionally and otherwise, could be a way to understand these new desires. I met with the couple over dinner at their place last Tuesday night. Their dynamic was fascinating, both had been in swinging relationships before, whereas I was stepping into it for the first time. We discussed boundaries, consent, and respect, ensuring that everyone involved felt safe and understood. As we spoke, there was an undeniable attraction between me and the wife; she's a beautiful woman who has always captured my attention from afar. Later that night, as we watched films together, the air was thick with unspoken tension. We decided to take it slowly and agreed on some ground rules, no physical contact at this first meeting but rather focusing on building trust through conversation. Despite these rules, I found myself struggling against the desire to reach out or pull her closer. To my surprise, she shared that she had felt similar moments of longing. Her husband remained supportive yet detached throughout our interactions. This complexity made everything feel even more delicate and emotionally charged. The night ended with a kiss on the cheek from both of them as they walked me to my car. The drive home was a rollercoaster of emotions, excitement mixed with guilt, confusion about how far I'd be willing to go, and fear of damaging what I have with my fiancée. Reflecting now, I'm unsure if I acted out of genuine exploration or because these desires feel new but also compelling. Is there something wrong with wanting more than monogamy offers, even in a deeply committed relationship? Am I the asshole for considering this path? My question to you all is: how do I navigate this desire without harming my partner's trust and well-being? Can swinging or non-monogamous relationships work when one person isn't fully on board at first?