Partner and I have been together 7 years, and really open for the majority of it with breaks throughout due to COVID etc.

There have definitely been bumps during it all. Dishonesty, boundary crossing from both of us.

During it all I discovered I was demi sexual and he is not. With his consent I approached a mutual friend to pursue a dynamic. They agreed and we've been seeing each other for about 6 months, and it's been great. He has had no shortage on partners and it's been nice to have a consistent person for myself. My FWB is well aware and has no desire to replace my partner but we're very happy and feelings are there.

As stated we were friends, hung out socially. It has become increasingly difficult for him to be around this individual. We recently spent a weekend away with his (my FWBs) family (purely as a couple and friend) and something snapped for my partner.

He no longer thinks I should be with my FWB, that it's too close. He still wants to be open, but wants me to find new partners to engage with. He regrets ever agreeing to allow me to pursue this but I've never had a say in the partners he's been with. I hate trying to find partners and really like the dynamic I have. I don't want to have to start from scratch. I suggested we speak to a therapist to try and find a balance. He's uninterested. He says if he can't shake this feeling it's the end.