Wow, Reptigal, I am sure you are just reeling and your emotional pain is thru the roof! Many hugs.
Did you and your fiance have a date set for the wedding? Is it possible he is having cold feet around that? I assume he is close in age to you?
Now as for this new OW in your life, he has gone about this very badly. Sure, he'd love a hot 3way sex scene with his gf and his new crush. That's the most common male fantasy out there. Unfortunately the reality is rarely as nice as the fantasy, unless you are an experience swinger with lots of boundaries in place.
Is the new girl also interested in a 3way sex scene, or actual emotional/sexual relationship with YOU? If you're not bi, and yr bf knows you're not bi, it's stupid of him to suggest this arrangement.
It's also quite rude of him to just get infatuated, announce it to you, and then spend tons of hours with the new girl, as you stagger around and have your entire world rocked.
Most mono couples that succeed at opening their relationships take things very slowly, at the reluctant partner's pace. Your bf needs to stop thinking with his dick and have a reality check. This isnt poly (yet), it's basically cheating with a little nice language tacked on.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37