Am I guilty of an emotional affair?

I've recently found myself in an unexpected dilemma at work. There is this co-worker that I've always thought cute and charming. It had always been casual for us at the office, like eating and chatting in the lunchroom, etc. until that one day we got a bit closer than usual (nothing physical). We've then become FB friends. I like the guy and we both enjoy each other's company seemingly. However we're both married and I can't help but feeling guilty for having crossed the line into the friend zone and for thinking of him too much lately. Is this an emotional affair? There is no chance of us just getting to know each other and remain platonic, is there?