JenJen,
It's so hard to function when sleep patterns are chaotic. I know it was one of the most difficult issues to address for me related to depression.
I make it a point to go to bed at around the same time and get up at the same time, weekdays and weekends. I also listen to relaxation CDs at bedtime to help me go to sleep. I'll admit it doesn't always work. I still wake up too early, and too often, but I think it helps. I'm less tired during the day, even if I didn't have a perfect night's sleep.