Getty

Diddy 's ex-girlfriend "Jane" is testifying in detail about how she says the freak-offs worked during their 4-year relationship ... zeroing in on a male escort with whom she says they routinely hooked up with and paid for his services.

Jane was taking questions on the witness stand from the prosecution on Day 18 of the Diddy trial ... and she brought up a man known as "Sly."

She said she and Diddy were impressed by images of "Sly's size," prompting her to reach out to him via Instagram.

Jane said Sly responded, and they began communicating ... with Jane telling him she was a "fan of his work."

She said she offered to meet him one day, which led to her jumping on a FaceTime with him and Diddy.

Jane testified the three-way convo turned "hot and steamy," and she asked Sly to exp

See Full Page