Well, I for one am confused at how this whole experiment has gotten to this point-- kind of a stalemate. Maybe lostinlove is being more open about details and the deep real issues going on in DMs, with dinged and others? If so, I don't know how anyone on this thread can offer any pertinent advice.
I've read here about a couple that met in high school at age 14, married at 19, had issues along the way that Lost thought had been addressed and resolved (but apparently were not).
However, for unstated reasons, this couple decided to start "swinging," in the form of (ideally) male/female/male sexual threesomes, which could possibly also include Carrie occasionally having one-on-one sex with males, and Lost having one-on-one sex with females.
However, what has happened is that Carrie has entered into basically a monogamous relationship with Leo. Meanwhile, Lost began to date a female he wanted to pursue, but Carrie got so upset about this, Lost immediately broke up with said woman. (What's sauce for the goose [the female] is apparently not sauce for the gander [the male], aka a One-Vagina Policy, and Lost was quick to capitulate.)
Now, Carrie is so into Leo, she has no interest in having physical intimacy with Lost, from the merest friendly gesture to full-on sex. Also, she wants to get her own place. They may divorce.
Lost seems to accept the fractured state of their marriage, and is willing to be downgraded to a friend with benefits of his own wife.
He is feeling very deprived sexually, but is apparently not interested in getting back in touch with that woman he was interested in a short while ago. He is willing to settle for sexual "scraps"-- being FWBs with his own wife-- if/when she feels in the mood to deal out such scraps.
And here we are, at least, as far as I can tell. I don't understand how, and especially why, things have come to this, other than that a relationship they began at age 14 has now run its course at age 39, and "swinging" was considered as a Band-Aid, but went all wrong. Perhaps, having gotten married at age 19, Carrie is now regretting missing out on having dated more people as a teen and 20-something, and is now dating a 20-year old to reclaim that era of her life. Perhaps the passion she has for Lost once, has fully fizzled, and certain aspects of his personality are just too annoying.
I mean, I can relate. I met my ex-husband at 19, married him at 22, and we divorced after 30+ years and 3 kids. We'd definitely grown apart, no longer shared enough interests or life goals, etc.