At this point (4 months separation, 1 year of having real M problems) Hubby firmly insists "No". I still have my doubts, but that is ingrained into my personality.
I suspect EA at least, if not a PA, with 25 year old personal trainer.
HOWEVER, I assume you ask this question to us all because you are "FISHING". I'll tell you from experience, BACK OFF from this question eating you alive! Take it from me it can ruin everything.
Sit down and soul-search. Figure out what it means to you. Will you still love them and want them if there was an affair? Make up you mind right now and move forward. The details do not matter.
My husband left and I went crazy, it "reaffirmed" all my fears and I went nuts during our separation (I have known about the personal trainer for 9 months prior). I got totally out of control when I should have been focusing on the marriage. I made a mess of things and showed my husband the worst side of me. Especially since there was no affair! My behavior drove him away even further.
Don't worry about the odds. Worry about what it means to you and WALK FORWARD. Plenty of people survived affairs (even imaginary ones) and went on to have better marriages.
ME 40 HIM 48 Married one year. First for him Second for me Proud parents of a baby girl