I have dark days sometimes too. I really think mine are hormonally related. Hormones are assholes, and they like to do a big shift at some point in the beginning of each decade. Having that knowledge doesn't help a lot, because it isn't something to readily fix, but on some level knowing does help. I hope your moods level out, whether hormonally related or not. One think I often think is that we go through phases constantly, and there is a good chance in a few years this issue will be a memory.
Cool picture, by the way.
I'm sure it is some sort of serious chemical imbalance, considering other health problems. And hormones are a bitch, everything seems to effect them, and they seem to effect everything. All you got to do to fix it is eat super healthy, sleep well, exercise regularly and have zero stress in your life, so easy. Oh and also, live in a suitable climate, not too hot, not too cold.
If I seem frustrated by this, I am!
Yep, that's what is so ridiculous about healing. It's next to impossible to have that balanced and healthy of a lifestyle. Apparently things do get better though, it seems to happen all the time.