I hear your pain and feel for you. This stuff hurts! I don't THINK there is an OW atm, but H had a PA 14 years ago so I know some of what you're talking about. I got the whole "She fills a void" speech H didn't leave for her, but pined for her, or as he told me at the time, any woman who wasn't me. (How can they even SAY that kind of stuff? Mind boggling.)
I don't think you're supposed to "compete" right now. Supposed to work on being the best damn Dumpling the world has ever seen and pay no attention to the alien who resembles your H. Once the intensity of H's OW wears off (and you know it will), and like a child who learns tantrums don't get your attention, H will look around to see what's what. And there you'll be. Rockin' the show.
Of course, none of this is easy. And none of it is quick. So hang in there, and be fabulous!
Me 46 H 56 M 22 yrs S22, D20, Twin Ss18
You teach people how to treat you by what you allow. What you stop. And what you reinforce. ~~~~~~~ A lack of boundaries invites a lack of respect.