Should I continue flirting with my coworker?

I've been working with a guy for a year. Our relationship has developed to where we talk often, we play stupid tricks and jokes, he hangs around, we talk on the phone at night if we're playing online games, which is often. I've recently broken up with my partner of eight years and he's been with his girlfriend for the past three. At first it was a playful flirtation but now I often find myself thinking about him. I am intensely attracted to him. Sometimes I get a strong feeling from him but i've been known to assume too much where there was too little. Anyway, he seems to be a loyal guy and I couldn't allow anything to happen between us.....so should I just stop right now? Or do I keep playing our little game which is so fun but could get dangerous? If he has no intentions of being an infidel and I'll never make the first move , is what I'm doing wrong?