[FMM] I [20F] tried to have an open relationship with my fiancé [23M] and my ex [20M]

Alright here goes nothing. My fiancé and I have been together for 5 years. Once in awhile in the bedroom we will talk about having a threesome with another man or being in an open relationship. Specifically with a man bigger than my fiancé. Now my fiance isn’t small by any means, he’s 7.5″ and thick but this has been our fantasy together. That got me thinking… my ex from 6 years ago has an amazing cock. 10″ long, nice and thick. He has a six pack, 6′ 3″, brown hair, blue eyes. When he posts photos of him in a suit, I melt (did I mention he is a model?). Then there’s me. 5′ 1″, DDDs, toned ass, not super skinny but not chubby, and I usually dress alt/punk, sometimes goth. He’s more casual wear. The crappy part back when we were dating? We never fucked. I’ve secretly always thought about fucking my ex and I started to be more open about it with my fiancé within the last year or so. I had a dream about fucking my ex a couple of times and here’s my favorite one.