Shortly after we married, my wife let me know she wasn't having orgasm with me in her. We were discussing our fantasies together in bed, and one of hers was to have full sex with a coworker she really liked and had orally serviced before we married. It was matter-of-fact statement in a way and while I was somewhat embarrassed, I was turned on by the idea. It wasn't a "size" thing as one might imagine reading the posts in this forum. It was about orgasm and technique. The way my wife phrased it was that she'd be turned on by an mfm threesome. He became a regular - every few weeks in our home, for a few years. Started as threesomes with me involved, then she wanted privacy with him while I slept elsewhere. I sometimes made breakfast for all three of us in the morning when he could spend the night. If you haven't experienced "morning after" interaction with your wife and her lover, you are missing out!
A couple of years into our marriage (as this first guy is becoming of less interest to her) she told me she was going to invite an attractive married black coworker to her hotel room after a company event about 200 miles away. As it turned out, she'd already had sex with him before we married - she 'fessed up! We'd had a couple of drinks, I had an erection, and she opened up and shared with me that this man always made her orgasm - in her words "sometimes in the first five minutes he's in me." I asked her about size (I had to know....) and she simply said: "You're not in his league." On a couple of occasions, she called me and left the line open so I could hear them. I guess that's "humiliation" - I felt it as I lay there alone in our bed with my hard cock sticking straight up as they fucked. Their dialog while they had sex was what was humiliating. The good news? Two items: this became a once a month thing for almost a decade, and 2) She and I are still together 30 years later and would do it all again. It's been a good ride.