Poor OW, her A partner is cheating on her with his W! She'll be p*ssed!
Sounds like typical WAH behavior. There are different voices in his head- his logic tells him he's making a mistake, his emotions tell him to pursue the OW and leave. He's testing both worlds to find the "best deal" for himself.
You dropped your guard and he moved right in for a piece of cake! No worries, mistakes happen. You caught yourself and have learned from it. Repeat to yourself over and over- "I'm forcing OW to meet ALL of his needs. As long as I continue to meet some of them, the A will last just THAT much longer!".
Go to the gym today and punish yourself with a hard workout!