Specific fic! I can't remember the title but the Winchesters were working together, Papa John was there too, and they had managed to gank the witch I think but she managed to cast a curse on Dean. He woke up the next day the splitting image of his mother and Sam was the one there with him, John was out when the curse struck. 
So Sam freaks out about the lady in the room while Dean doesn't get it until Sam points it out that he's a chick. Dean goes into the bathroom and stays there for loner than usual, silent.
Later John comes in, sees Dean and after an attempt can't ignore how much it just hurts to even look at Dean before he leaves. Dean is crushed, becomes mute and sinks onto the floor because he was the reason why John left. Sam holds him in comfort and Dean still doesn't make a sound when he is shifted back.
The curse was that silence was payment I think....

Found it was! Found it was!! In the first comment below! (screwed up some of the details though...)

A few general requests:
1) Are there stories where Dean is cursed to become female or look like his mother that does not end in Wincest? 
- Dean can remain as a woman or he changes back to manly Dean!
2) Dean was born a woman and gets pregnant (Not through the Winchester men please)
- Dean can choose to keep the baby, give it to someone else or suffer a miscarriage leading to angst
3) Are there any fics that have parental!Ellen towards Dean?
4) Mermaid/merman Dean?
5) Feral Dean

No Wincest please... Or if it is really good (as in disturbing or just plain good), give me a heads up please.
Destiel, Debriel & Dean/omc is a-okay with me!