Ever considered you may be suffering from sleep apnoea? I was sleeping properly (apparently) for about 10 hours a week and feeling tired and crap most of the time until early one Sunday morning I fell asleep at the wheel and hit the central crash barriers on the A1. My GP then took an interest, got me fixed up fairly quickly with a CPAP machine and I've been fine since. It's a bit of a nuisance at times, but it's made a big difference to my life.
No its not sleep apnoea mate. Two of my mates suffer fron that and both have cpap machines. I just lie there wide awake.