Sounds like you have what I have real bad, SAD. I was thinking that from the start because it is very common (even if mild in most cases) and causes the apathy and sleepyness and all the other stuff as a result. Look into a small dose of melatonin (1-3mg is what I use usually and it helps, especially at first). Also you should get up early and go to bed early and no naps (even though they are ohh soo good)!