Yup, my H had the seeds of an EA already planted (by probably a month or so) at BD, and I even said something to him just days after BD about thinking he was interested in someone. Something like 'Yeah, I know it's stupid, but that's what I thought.' I clearly remember he sat there like a deer in headlights, and said absolutely nothing. That should have been my first clue. Turns out I was not stupid at all - I was dead on. But it took me about 8 months to finally dig up proof. The Internet can help you, and it can seriously hurt you, too. He was flabbergasted that I figured it out myself. I told him 'It was easy. I was your girlfriend once.' Pow.
Me 53, XH 57 M 20 (+1.5) years, no kids BD June '13 H moved out July '13 Confirmed long-suspected PA Feb '14 H filed for D Nov. '14 D March '15