My (46M) wife (44F) asked me if I wanted to fuck other people.

Long story but I will try to keep to the main points. I will start this by saying we have been married for almost 20 years and I have never cheated.

One day a year or so ago, my wife and I were alone on a dock having a couple of drinks. My wife out of nowhere asks me if I've ever wanted to have sex with another women. I thought she was joking or she was testing me at first. But when I pressed her a bit she was dead serious. I turned it around and said "you go first, I need to think about this". As soon as I said that she brought up a guy from a party we went to a few months before. Like she brought him up INSTANTLY. After she went I was kind of shocked. I didn't have an answer for her, there is nobody that I could think about that I wanted to have sex with. I'm not some prude either, I look at porn like the next guy but the thought of actually having intercourse with someone else really never entered my mind as a possibility.

I was obviously pissed off but I kept my cool that day. I kept it inside for a while and brought it up to her. The more I thought about that party the more upset I got. At the party she did talk to this guy A LOT. And at one point I left with a group to get more beer. When I left she stayed at the party and so did this guy.

When I brought it up to her, she claimed that I am making a big deal out of nothing. That she didn't even like that guy and that it's just the first thing she though of. She claims that she asked for me, that somehow she wanted to see if I was thinking about other women.

My brain can be pessimistic and think the worst. Am I over reacting in thinking that my wife wants to fuck this guy? That maybe they did ot that maybe something sexual happened. I mean, why bring something up like this unless you have a guilty conscience??

OP EDIT: First, thank you all for the comments. I wasn't expecting so many responses. I'm still reading through them all. It's sorta a reality check here to hear my fears confirmed by so many. Again, thank you for the responses, even the ones that hurt.