Nope. But I have helped other people cheat. Does that count?

Nope, never even had a girlfriend. =(

When I was a thirteen year old, yeah. It doesn't count when you're that young though, you're still just a mindless hormone driven kid.

I wouldn't dream of doing it now. I don't think I would have seriously thought of doing at any point in my adult life.

What no story?

In 6 years and a half with my current gf, the thought of cheating on her never crossed my mind. 

I've been on the cheated end with my first girlfriend and it stings like hell, so I wowed to myself that I would never put anyone in that position, it's as simple as that.

hello,I'm 30 and never had girlfreind,bye now. lol

really?

It feels normal after the first time.

Wouldn't be able to live with myself

I used to be really faithful. Then I began cheating on a girlfriend (my 6th I think) after we had a big fight. We didnt break up or anything and remained together for several more months. After that I never had any qualms about cheating on the girls I dated, at least not until a few years ago. Though I never got caught nor had to own up to my actions I kind of just grew up. I decided that was not the kind of person I wanted to be. Haven't cheated since.