I played through Penumbra Overture and Amnesia Dark Descent. Amnesia really got to me, and I had to start playing it in the daytime with the lights on and my wife around to laugh at me and ease the tension. No one should be ashamed about being afraid because of these games, after all, that is the point of the game.
As far as I know you won't find any other games where you really can't fight back and are always on the edge of your seat. Most other 'scary' games give you the ability to fight what attacks you, such as Bioshock (spooked me the first time I played it) or Dead Space. I'd say your best bet would be Resident Evil 5. I know some people loved it, but with it's broken controls and inability to move and chew gum at the same time, you might as well be helpless. Not really scary though.
Again, I think your best bet is to wait for a sequel to Amnesia.