Krista and I were engaged early, freshmen in college. During the first semester of our sophomore years, I began noticing changes. Krista would sometimes be distant. Other times, she'd be late to a date or other event. Usually a lame excuse accompanied. A few times she was absent/AWOL for a night, again with lame excuses.
In parallel I began hearing rumors that Krista was fucking around on me. Inconsistent, inconclusive rumors, but still. I lived in denial. Then one day, Krista broke off our engagement, handed me back her ring - she dumped me. Didn't want to talk about it.
One of the more consistent rumors was that Krista was fucking this dude, Monty, a frat boy that was loosely in our social circle. I knew his cock was bigger than mine, as I'd seen him nude a couple of times at lake parties. He was also rich.
No matter what I tried, I could not break Krista's spell. The only way I could get hard and cum was thinking about Krista fucking other guys, especially Monty. Along the way, I got more rumors about Krista; someone spied Krista sucking Monty's cock at a party... someone saw them in the back seat of her car, fucking... It drove me crazy.
Then, I had no idea what cuckolding even was. One night, I went to a female friend's apartment - she was going to give me pity sex, having noted I was pining away for Krista. I was unable to complete the act, even though I tried visualizing it was Krista I was trying to fuck.
I ended up on her sofa. There was a pile of magazines on the floor. Mostly soft core pore, Playboy, Penthouse, and the Forum mags. I picked up one of the latter. One of the stories was about a couple trying out cuckolding. The female half was narrated as a match to Krista. I read, and re-read the story, cumming over and over. My friend caught me early the next morning, still jerking. It was so fucking embarrassing...
I knew from that moment that I was a cuckold.