Found: Sterek Derek has nightmares.

[callmekginfinit]

Hey Guys, I'm looking for this fic if it's still available on Ao3. It's pretty short where Derek has PTSD nightmares and regularly scentmark Stiles and count his fingers and Stiles' fingers. Thanks hope this post does not violate any terms and agreements.

Found it: https://archiveofourown.org/works/1460506