Caught in the Moment

I'm a college student and I've been in an open relationship with Alex for a while now. We both agreed to be honest about our interactions with others, but lately, it's become harder to keep things just friends. Last week, after a few drinks at a party, I found myself alone with another guy from my class. The way he looked at me... it was intense and unlike anything Alex ever does. Before I knew it, we were in his room, exploring each other. It felt like the moment of truth for both of us, but now I'm left wondering if this is just a phase or something deeper. What should I do? Is this normal?