As anyone will tell you, you can't truly love others until you love yourself. Even RuPaul says that as her tagline at the end of every episode of Drag Race. "If you don't love yourself, how in the hell can you love somebody else? Can I get an Amen?"It's not that sex is off the table, it's that I'm sharing this incredibly precious thing with others, with people I don't feel deserve it. I have put half of my life into taking care of her, loving her the best I can, and these are just people looking for a goddess for their fun. I'm probably not being fair to them, but it's how I'm feeling right now. I feel left out. I've always felt left out, like I don't belong anywhere. I what to feel included, I want to feel wanted, I want to feel beautiful, and I don't at all. I know I must find it within, but I've hated myself for so long, I don't know where to even start.
That's where I believe you should start. You can work on your own self-love. The hatred surely stems from your childhood. Your parental figures probably told you you were worthless. It's time to move on from that.
If you don't love yourself, and your self-esteem is bad, you will cling to friends and lovers as if they are a life raft, holding on to them desperately. This is self-defeating. They may be okay with their role as your rescuer for a time, but it can start to feel like a burden. That might be why your wife is pulling away by getting involved with ENM. She might be quite tired of being your "everything." That's draining!
Rather than trying to glom on to her lovers, or even seek your own partner, I'd start with the inner work you need to do. I think Bobbi here recommends book (maybe a podcast?), Unf*ck Your Brain. And of course, you can go to therapy or self-help groups.
There are ways to grow your self-esteem which usually involve behaviors that make you feel accomplished, powerful, helpful, be they hobbies, volunteer work, a new position at your paid job, raising children well, traveling independently and learning new things, etc.