Should I ask if he's having an affair? Even if he is, he'd just lie.
Exactly. He won't be honest about it and he'll try to shame you into apologizing, so there's no point. Rule two: cheaters lie.
If you suspect an affair, gather intel any way you can (cell phone bills showing a lot of calls or text msgs?) but there's no reason to let him know that you suspect anything until you have proof.
Me: 44, Wife: 39 M: 17 years T: 20 years Bomb on 08/25/09 1/13/10: MC started 1/28/10, 2/8/10: More bombs 8/28/10: Wife moved out No talk of D, no movement