You were at a sleepover at your friend's house, Kayley. There wasn't enough beds, so you had to sleep in her brother's bed while he was out at a hotel, therefore, he wouldn't know you slept in his bed. But...in the middle of the night, of course...you got your period. You got period blood all over his sheets.

i was on pinterest and saw a comment that told a story that was kind of like this! [F4M - fem pov since it has your period...but you could always be trans mtf] sorry, i'm just used to fem pov bots...