The last Flight International magazine I saw a couple of months back there was an article that NASA is concerned about the lack of reporting of fatigue, human error, and other aviation events by pilots.
There's nothing new about this and I'm surprised they're surprised. Fact is you are required to fall on your sword if make a mess of things and so you should, but in many cases airline management arent amenable to some pilot reports and fatigue tends to be one of them.
Report you are fatigued too often and the result will be a visit to the office where you will be asked if you're in the right job.