Are you sleeping enough? Are you getting at least 8 hours of sleep every night? If you are, are they consistently at the same time? Is it possible you need more than eight hours? Do you get woken up during the night? Are you a light sleeper?
I think that someone (maybe Rav Avigdor Miller), whenever anyone complained of depression, he said the first thing to do is to make sure you are getting enough sleep. I know that for me that is very true.
Of course, there are many other possibilities, but I think that lack of sleep must be ruled out first, IMHO.