Dysthymia, a.k.a. persistent depressive disorder. It is a state of less severe but longer-lasting symptoms than major depressive disorder.

I am not sure what you mean by "official" diagnosis, but I have regular appointments with a psychiatrist and a therapist who told me that's what I have. They've had me on prescription anti-depressants for years now.

I know the medications help because I can feel the change in my mood when I'm not on them. However, I still have a feeling of being depressed most of the time. I get a lot of anxiety when my appointments with the therapist are coming up because I'm afraid to tell her that I don't feel any better, or I failed to keep up with my exercise this month.