Hi, I also read your other thread. Triads and quads are so complicated, it can be super hard to negotiate everything and get everyone on the same page, emotionally, plus have everyone be sexually fulfilled.
It sounds like your fiance is in NRE with the gf and wants to have sex with her more than with you, for now at least. This is one of the tough things NRE (new relationship energy) can do to poly folk, which is a bad thing for the primary partner. I hope you can communicate this to your fiance and let him see loving polyamrously means everyone's needs are important and all partners should have needs taken care of.
Now, the bf, you say, is a swinger. He seems to be more sex-focused than love-focused. He doesn't love you, and he doesn't want to keep your quad closed. That's his right, of course, if those are his desires, you can't force a square peg into a round hole. It must hurt though!
Also, what is this about your fiance lying to the gf to get what he wants? That is a red flag.
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