looking for a story

I saw a reference to a story on another site but it didn't give the author or the title, it just made reference to something that was "just like that story".

The reference was to a boy who had gynecomastia and was required to wear a girls swimsuit for a swim class at school. He was then invited to a party by one of the girls that turn out to be a swim party, which she hadn't told him. She loaned him a swimsuit which he wore at the party with the other girls. Then was invited to a sleep over after the party.

I know I've read the story, but can't remember the name or the author.