Sickness,Depression, Fatigue or Laziness?

Today I got up at 6 am as usual to get the kids off to school. Afterward I spent several hours doing some computer stuff, part of it was for work, the rest wasted on FaceBook. By 10 am I was so sleepy I didn't think I would be safe to drive to work. Finally by 11 I succumbed and went to sleep, sleeping until 2 pm.

It is now 10:30, and I could easily fall back to sleep again right now. I'm not sure why I'm so tired all the time. Over a month ago I caught a virus that caused a slight fever, sore throat, stuffy nose, and cough. It is the cough that gets to me. Every winter when I get a cough and that darn thing sticks around forever. I've now been coughing for over six weeks. When I have a really bad coughing fit I'm exhausted, so is that why I'm so tired?

I also suffer from Seasonal Affective Disorder (SAD) and living in the Northwest isn't the best environment for me. (I should've moved to Arizona.) This causes me to be depressed in the wintertime. I can also be depressed in the summer, it is just worse in the winter. Depression causes me to be tired all the time, to want to sleep all the time and to let my house become a disaster.

Also because of being sick and the cough and the depression I haven't been getting any exercise. This could be another reason for my fatigue. However, I find myself too tired to even think of getting some exercise.

What to do? I'm too tired to do anything but sleep, and all of this sleeping isn't helping. I know that if I actually got some stuff done, like cleaning the house and getting some exercise then I'd feel better, but it seems like a Herculean task.