I think I'm depressed....I haven't been depressed since I was 19!

I am just in a funk, my thoughts are negative all the time...I dwell on the negatives in my life, and think the worst of myself, feelings of worthlessness.....I've been staying up most of the night and sleeping in until 2:00 in the afternoon for a couple of weeks now. I've tried talking to my therapist about it thinking that if I just had some self disciplen or something...I am really struggling to fix it.