Please help me find a story I read ages ago!

It was probably at least two years ago. It's a story about two college students, male and female. Things happen and for story reasons the girl begins to squeeze the guy's balls with her hands under the desk during lectures to see his reaction and get off on that. One day she's masturbating as she's squeezing and starts squeezing really hard--too hard. He says their safe word but she doesn't stop and ends up crushing both his balls.

If you can help me find this story I'd really appreciate it!