Past self-harm Reid

Hey people, new in the comm here =)

First of all, I apologize for any mistakes I may make while writing this. English is not my first language, so...

I need your help finding a fic. It was a Gen one-shot where the team was on a case. They were on an interview whit a guy (I don't remember if he was a suspect or not). The thing is Reid goes in and starts talking to him, The guy was on self-harm and I remember him telling Reid he wouldn't understand why he does it. And Reid answers that actually, yes, he can, and starts explaining his own experience whit self-harm.

At the end he comes out of the room and the team asks him why he didn't tell them, And Reid just tells them 'You wouldn't understand'. 

And that's it. 
Thank you in advance =)