Nate, first of all, I hope you have had a recent physical exam, and then also asked your MD to determine if you have clinical depression. A bad case of the "black awfuls" can have a biochemical cause, and medication can be effective. Some people have also found that yoga is helpful. Clinical depression is a medical condition, not a personality issue.
If you do not suffer from clinical depression, I would only then move on to astrological analysis. You are "majoring" in the 12th house in this lifetime. This house of "self undoing" seems to have two successful expressions, from everything I can gather about it. It does seem to mean dedicating one's ego to a higher purpose, because with your sun in the 12th, it is the identity that gets "undone." Some widely recognized people with a 12th house stellium such as you have become deeply spiritual people (philosopher Teilhard de Chardin was one.) Others become very altruistic humantarians like Mother Theresa. You may be involved in a "serve or suffer" lifetime. Service to a higher power if you are at all religious, or service to people who are misfortunate in some way, if you are not, would seem indicated. The 12th is identified with people who are shut-in in some way, such as in hospitals and prisons. Consequently, volunteering at a hospital or hospice, or even at a prison (such as via the John Howard Society or Elizabeth Fry Society], might be beneficial for you. I have to ask, how are you manifesting your 12th house now?
Then you have a T-square involving Mars, your moon, and Pluto. This to me seems like a recipe for your feelings (moon) taking a beating (Mars/Pluto). Ditto for your Saturn/Neptune square, which can shake your sense of self-confidence. Juiter retrograde can also make you feel more serious about life.
Bot wow! You have a huge "yod" configuration in your chart, involving Jupiter sextiling Uranus, and pointing to your Mars/Mercury. Jupiter sextile Uranus suggests that new and unusual things and people can be a source of enjoyment for you. But their discharge into Mars and Mercury in the 12th suggests to me that you may wish to pursue a spiritual philosophy of some sort, or perhaps spending time in nature through hiking (Mercury/Mars) or some other wilderness activity that gives you time to commune with your solitude (12th) in a positive and beautiful setting. I have to wonder, are you getting outside much in the sunshine and fresh air? Your north node of personal growth in Leo in the 3rd house positively needs it. Nobody's morale can stand being indoors too much.
Astrology isn't an exact science (at least not in my hands) but see if any of the above resonates with you. Then I would just suggest you start with baby steps. Little by little, you may find things improving.
With all good wishes for your journey to wellness, Waybread