Can’t stop thinking about it..

Ok so I have an issue. Lately I’ve been like super horny and it’s been causing me to think about different things, specifically a threesome. I love my fiancé with all my heart and would never in a million years cheat on him or put him in an uncomfortable situation, so let’s clear that up real quick. Anyways, I’ve been having the overwhelming thought of sex with him and another person. I brought it up to him and he said that he just wants me and no one else (😩😍), but I told him if it’s something we would both be okay with as a one time thing, then what’s the harm? I’m 99% sure it will never happen, which I’m totally okay with, but I can’t stop thinking about it. Like if it did happen, who would we do it with? Another girl? Another guy? One of our close friends? Has anyone here had a threesome? Who did you do it with? Did it do anything to your relationship? Tell me your stories 😩😩😩 Please tell me I’m not the only one who has thought about this😂