I was asked to post updates to this:

https://www.reddit.com/r/asktrp/comments/6oe8gc/sexual_fantasies_sex_life_with_gf_spinning_out_of/

Nothing has happened yet, not like you're thinking. But I brought up that it made me feel uncomfortable where this was heading, like the people on the other sub suggested.

She said she understood and that if I wanted we could stop. But she also reminded me that last time she stopped when she saw I was apprehensive, and yet it was me who brought up X again until he became part of our foreplay and fantasy life. She says I'm sending her confusing messages and will stop but wants to know what to do if I bring him up again or if our fantasies start veering in that direction. She said she cares about me and would do what I wanted but did mention that it might be fun for both of us if we actually went through with it, which surprised me that she'd say that openly.

I'm ashamed to say that after this talk we continued the same as before, because of me. I kept goading her on about him and while we fooled around we talked about how hot they would look together and other stuff like that.

The truth is I would like to continue this as a fantasy with her, but not for it to go anywhere else. She did say we don't need to actually carry out this fantasy, but during sex we both say otherwise. I'm concerned about where it's going and how I can stop it only at the fantasy level with her.

Another element is that she said that X told one of her friends from the gym that he thinks I'm gay or bi, which is not the case. She teased me about this during sex and it turned me on (not because I'm bi but because it turned me on to have her talk that way about him) but then it made me angry that he'd tell people this.

I met him at the gym again today and didn't bring this up, but he seems to be turning up the pressure in terms of wanting to set something up with my girlfriend. He changed right in front of me again in the locker room, basically in my face, and talked shit about her and at the end asked if we're all going to get a drink this week. He suggested we all meet Wednesday but I didn't agree.

I'm not stupid. The question is if I should break up with her or THREATEN to before anything happens. Or if there are any subtle ways I can make myself superior to or more attractive to her than this guy, while allowing the occasional unusual fantasy.