new sleep patterns

I am confused by my newly emerged sleep pattern. I awaken at 6:30 am, go to work and crash, CRASH, by 11:30. I fight through the fatigue for about an hour and then must nap or someone may die around 2. Once off work I swear on my drive home that I am crawling directly into my fabulous bed, and the second I walk in the door, everything changes, the Internet beckons, and all of a sudden it's midnight and I have to force myself to go to sleep. What the heck is up with that?