You were adopted by John after he found you while he was on some mission. He decided he couldn't leave you. He was reunited with his sons, Sam and Dean Winchester who you met then. They didn't really like you because it didn't make sense that John had the heart to keep a kid with him when he couldn't even take care of them during all those years after their mother died

After his death, Dean and Sam didn't leave you to some foster home. Instead, they took you with them. You tagged along on hunts and stayed with them in hotel rooms or hideouts, you didn't do the hunting and the brothers kept you out of danger

You never confessed that you felt safe with them even if the three of you weren't that close

One night, you got your period while you were traveling with them, great

" You need anything? " Asked Dean as he pulled over at the gas station to which you said no

He and Sam left to go get a few things and maybe go to the bathroom. You got out of the car and went with the small amount of money you had, buying snacks and the biggest pads you could find

You went to the bathroom after that and got in the car just before the two returned. The snacks were stuffed in your hoodie

" I thought you said you didn't need anything"

Dean said as they returned, noticing that you've been out

" I just went to the bathroom " You covered it up

A few minutes into the drive ( let's pretend the car had a backseat if it doesn't )

Dean: “Alright, enough. You’re sittin’ there like you swallowed a grenade. What’s going on?”

You shake your head quickly. You: “It’s nothing.”

He began getting impatient

“Don’t give me that. You’re hurt. I can see it.” He noticed you holding your stomach

Sam : “You don’t have to hide it. You can tell us.”

Heat rushes to your face. You: “It’s just… my period ”

Silence. Dean freezes. Sam blinks. For a moment they both look like you just recited Latin backwards.

Dean: “…Oh. Uh. Right. That. …So what do we—uh—Sam?” Sam: “Don’t look at me, I… I mean, I know what it is, but—” Dean: “You read all the damn books, how do you not know?!” Sam: “Not those books, Dean!”