Just after my college years, I was married for just over 3 years in the late '80s. I made the "mistake" of marrying a gal that was hot and very sexual. Over our three year marriage, she must have screwed at least 20 other dudes that I know of. It bothered me a lot the first 2 years because I was young and insecure, but I definitely knew what to expect by the 3rd year, and there weren't any surprises when she came home full of stink by then.
We had been married about 6 months when she first cheated on me (that I know of). I was at a party and sent one of my casual friends over to my apartment to get some of my CDs. After he didn't come back, I tried to call my wife, but she didn't answer the phone. I wasn't sure what was going on, so I caught a ride to my place...of course, his car was there in the driveway. I peeked through the window and saw him sitting in his underwear on the couch, though I couldn't see my wife. I walked into the apartment, and he hastily dressed and left, saying he was just there drinking my beer and he should go. My wife was in our bed. She denied that she had sex with him, got mad and refused to have sex with me that night, even though I was leaving on a 4 day trip early in the morning. I knew damned well that she screwed him, and she finally admitted to it over the phone while I was out of town. I was enraged and broke up with her right then. After the trip, we both moved our things out of the apartment, and she had some other dude helping her that I had never seen before. She definitely screwed him during our break-up, but she might have been with him even before then.
We were separated over a month, and I screwed several other women myself (including her sister, lol)..but she called me up and insisted that we meet to talk about getting back together. She wound up sucking me off in my car, after saying that she had just gone through a fling stage and I guess that convinced me to give our marriage another try
I trusted her over the next couple of years, but looking back, it's obvious that she was having sex with lots of other men, though she denied almost all of it. A few highlights:
-After a party, she drove a couple of dudes home as she was the designated driver. She came back smelling stong of men's cologne, especially on her breasts. I got pretty mad about it, but she denied anything happened. She did screw me that night, but I was really too drunk to notice if she was already used beforehand...she might have been telling a half-truth and just sucked one of them off or took it up the ass.
-She went to work one night, and I noticed her lingerie drawer a bit open. I inspected it and noticed that her sexy undies and fshnets were gone. The next day, they were back in the drawer, I never said anything to her about that.
-One day, i found a pair of her stained undies in the trunk of her car. They were a few days old but still smelled strongly of sex...she must have hid them there but forgot about them. I never mentioned them to her either.
-She went to garage sale to buy a refrigerator, and came back saying that the owner was very forward, promising to give her a good deal after squeezing her tits. She also said he had some porn tapes for sale, and went back to get them on my okay. Looking back, I figure she screwed him several times, though she told me she was just teasing him for good deals.
-She got the brakes fixed on her car, and when I asked her how much it cost, she said it was free. I was kind of catching on to her game by then and not getting too jealous about it. She later admiitted that it was a "cash or trade?" deal.
There were a lot of other things going on too, here and there, but I think I just stopped worrying about it because she always came home afterwards.
The turning point came on day in a store that we were shopping in. She had just gotten off work. In the middle of our shopping, she froze and proclaimed that we needed to hurry home because she started her period...she said it was almost gushing out of her. We got home, and after a trip to our bathroom, she said it wasn't her period after all, but that she was just "very wet." I saw her panties and it was obviously semen that had oozed out of her. At that point, it didn't really bother me...she took a shower and then we had great sex. We had a different kind of relationship in our marriage after that, but that's another story. But until that point, she must have screwed a different guy at least once a month.