Our Vee got off to a rocky start...Dude and I had a "cheating"-type relationship for 3 months before the shit hit the fan. And it hit pretty hard. Reconciliation required another 3 months of "no contact" between Dude and me and MrS. (You can read the whole sordid saga in my Journey blog here.)
You and your bf have been together for SIX times as long...I can only imagine what will be required to effect reconciliation, if it is even possible...
We were able to work through the "cheating" and rebuild our relationships with each other (all of them) - helped by the fact, I think, that I have always ID'd as poly and so this was NOT a new concept to MrS; and that Dude and MrS were already close/best friends before this happened...and genuinely care about and love each other (platonically).
If his GF is *amazing* you just might be able to work this out...but I wouldn't hold my breath and I would be prepared for the shitstorm that cometh...
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (23+ yrs)
Dude: hetero poly male, live-in boyfriend (4+ yrs) and MrS's best friend
Lotus: poly bi married female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe