Let me be the first to welcome you then. No you are DEFINATELY not alone. As I'm sure you have figured out by reading here there are many many of us, and a lot of us don't have to use photoshop. That's not my cock my wife is sucking on in the picture.
I don't know the percentages, of people actually doing it here, someone posted on that, but take it from me there are a lot. Once you are sure you can handle the emotions of another man being with your wife, why don't you sit down with her when you guys aren't being sexual and really talk to her about it. It sounds like she is just thinking you are saying it to turn her on right now.
Just make sure that your realationship is always most important. There really are some huge risks, but there is also so much pleasure. Every relationship is completely different, so to succeed make sure you keep talking and find out what works for you two. Reading what others are doing is great for perspective, but really when it comes down to it you guys have to love your own lives. Good luck. Look forward to seeing where you take this. Keep posting.