Engaged but Curious About Kink...

I'm engaged to my college sweetheart Sarah ... We've been together since freshman year, and we're both planning on getting married after graduation next spring. Lately though, I've felt this pull towards something different .... Like last night, while we were cuddling post-sex, the idea of being tied up and dominated by a stranger flashed through my mind... It was so sudden and unexpected ... Sarah wouldn't understand or be into it at all... Is there anything wrong with wanting to experience this once? Or am I just losing my damn mind? What would you suggest?