To me he is not "monogamous." He is in a polyship with you and C already. That's not monogamy then. To me he is "monoamorous." He loves you and only partnered with you.
Is there some guilt thing here to resolve on your end with that? Like it would be ok to give yourself permission to love C and DH if only DH also had someone else to "make it even" somehow? And because he isn't doing that, you are "stuck in guilt" and hello resentment toward DH?
It isn't only DH's having to do emotional work with "I am enough for her" kind of stuff and not going all off into the land of "Why's she got to have 2? Aren't I enough for her? " thinking patterns? He has "pre-decided" your rejection of him, so then it comes out in not wanting to initiate sex?
Maybe expand the definition of sexy time to be less pressured "sensual time?" Kissing, hugging, making out, taking showers together -- sensual
time. Could reframing it that way take the pressure off?
Maybe there's other baggage there in the emotional health or mental health department of the marriage. What about the spiritual health of the marriage? How's that? Because while there's sex problems, it doesn't sound like it relates to physical
health things like libido or erectile dysfunction or similar. It pops out in this area, but that's not where the root problem starts.
Maybe something like this
could help change the negative thinking patterns for each of you better than the therapist did? Something more "group" oriented than just you guys and the counselor?
I think if he were my only outlet for sexual fulfillment, I'd be more worried about the viability of our relationship. Considering that I do have C, I think I can work on getting back enough of a marital sex life that it feels close, happy, and natural. That's my goal.
It sounds like maybe you know what you want to do/resolve/accomplish but need help with the HOW of it?
But do you know that HIS goals are? For himself and for the marriage? And are they compatible goals with yours?
Emotional intimacy can happen not just through sex (physical intimacy) but through talking (mental intimacy). When was the last time you guys had a good heart-to-heart kind of talk?
I dunno if that helps any. Hang in there.