@Tynon_1221: you sure you do not unlock it by accepting Cedric's deal? In that case it's him the one in control of the body, you cannot do anything but watch. If I recall correctly, the condition I chose was for Cedric to free that man from the curse, but it could also work with kill the witch. Not with the first one, but this is just a speculation of mine, since I already unlocked it when I chose this option.
Hope it helps :)

I think "Everything is fine" is not achieved by watching the credits but is triggered by one of the possible ending.

The one where Faust keep control of his mind

You get 'Fluoxetine Doesn't Work' by trying to save Wagner by talking, but failing due to lack of manipulation.

I don't know why but I can't get the option to duel Cedric.

The only Achievement I lack is "In the head."

I did not get to 0 Soul beforehand, so that might have something to do with it (had 20 by the end, spent Soul at every possible opportunity, but I know if you want to get 0, you have to win the gamble with your cell-mate and then refuse to banish his soul from yours and even then, I think you still end up with 10 because the cop sacrifices some of his for you ; I was not given the option to duel with Cedric. It was either "Give all my soul to her" or "Take his deal."

Such a great visual novel, and I recognize that half the fun is finding all the paths on your own. At this point though, I would really appreciate a walkthrough on how to get this Achievement.

also for the happy ending chieve i made the following...started with 3 on charisma and 3 on motivation(the second one) didn't spent any of my soul(had 100% at the end),went to met the soulmate but i accepted the older woman offer after the soulmate leaves and chosed to duel cedric at the ending

Just don't have sex during the entire first chapter! You can have sex later and still get the achievement.

for the virginity protected you also need to refuse sex with the the girl from dark world...can't remember her name right now

Just a few clarifications:

"Virginity Protected
Refuse sex w/ women at bar"

You get this achievement only after the end of chapter 1. There's another situation where you can have sex in the first chapter.