Hi ACJ! I know how lonely things can get after a marriage breakup. Learnt that first time around for me.
The NG certainly is a diversion. Not too long ago, you were still saying you love your STBX. Remember how you burst out crying for now reason and you realised you still had feelings for your H (I think you always will to a certain extent --- father of your children, etc.). It's possible that the OW's pregnancy shocked you into realizing that there is no hope of reconciliation (not even the tiniest). Now, I know you've been alone for a long time, but not alone without being 'in love' and yearning after someone.
Just a thought.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim