I (M26) have been in a relationship with my gf(f26) since high school. It will be about 8 years now and we have been living together for the last 2 years. Everything was going great apart from a few arguments that happens to everyone in a relationship.

This discussion started when we heard a rumour about 2 out of the 6 couples(who we know as acquaintances and meet them occasionally on birthdays, anniversaries etc), who regularly hang out together, actually exchanged partners for a night.

Ever since we heard about this, I have seen my gf getting excited when talking about it. Calling things such as these very normal and happening all the time. Accoridng to her, it's ok for them to do it and spice up their love life a bit.

She hasn't outright told me that she wants to do it but I can sense it with the way she talks about it in a very postive tone.

AITAH for directly telling her that it's not normal for me and I won't ever participate in things such as these and if she even thinks she wants to sleep with someone else she should break up with me before doing that because I will never be okay with it.

Edit : I love her just as much she loves me and one day want to mary her. I don't think she will ever do it once I told her I won't. She didn't cheat on me, I don't think she ever inteded to cheat on me. It's just that I made my point and mentioned breaking up quite sternly that left her teary eyed which made me feel like an asshole.

Edit 2 : In 8 long years , we have never had any trust issue, not even a red flag. Simply nothing that could make either of us feel something's wrong. This discussion didn't just happen out of the blue. A mutual friend simply happened to tell us about the couple swap at a party whilst pointing to both the couples who were on the dance floor at that time. So people, who are actually suggesting that my Gf was probably already cheating on me and this idea had originated in her brain after she cheated on me, are wrong, it never happened. We both were surprised when we heard about it. It's just how she later reacted to the couple swap is what started to bother me. While I outright in my mind rejected it as doing that was not my cup of tea it probably gave birth to a new fanatsy in my gf's mind who would discuss the couple swap scenario with great excitement for the next 15 days. It was after probably the 4th time discussing how couple swapping is so common and happens all the time that I kinda snapped and went harsh on her to tell her that it's a strict "No" from my side.

Edit 3 : For people who are telling that it should be the other way around and I should be breaking up with her, the intention is not to break up. And what should I break up for right now? She hasn't done anything. If thinking was a crime, all of us would be behind bars.

What I wanted to convey was that, I will never be okay with her sleeping with someone else. It's just not me. And if at any point in time she feels she needs some one else to do it with, then instead of cheating on me, she should respectfully break up with me first. It was just a heads up.

Also I plan on having a conversation with her tonight. Let's see how it goes.