I guess I still just don't understand how my H replaced me so easily and found comfort in this OW.
H didn't replace you, and you are not in any way replaceable. You are reality and H is following a fantasy. It's not a replacement, it's a trivial distraction. Sooner or later that fantasy will become reality also, and at that point H will likely flee that too.
Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015