"The Girlfriend Experience", available for free on my blog.
"Norm is caught cheating and breaks up with him. She leaves with a warning that he is going to lose the only thing he cares about. With her gone, he has to scramble to find a date to the company party where he was hoping to impress everyone with his hot date. He resorts to getting an escort to come and when they start dancing they find that their genitals have swapped places! They proceed to have a wild night experimenting with their new anatomy while trying to hide it from the other party-goers."
The Smashwords version available here at "choose your own price", if you want it in ebook form or choose to support my work.
If you would like to commission me for a custom story, details are here