^^^Kiki is spot on.
I try to focus on 2 truths to help me get over the insecurity I feel:
1. Even with everything My fWH and MCOW supposedly had in common (career, interests, etc) it wasn't enough to take him away from me in any permanent way
2. What fWH and MCOW had together was shallow, false, manufactured, delusional, full of lies only they believed, and had nothing to do with reality
With some good, solid Time in R a closeness and intimacy that has nothing to do with common interests will become possible.
Take care of yourself. I hope you find peace.