While reading your post I was reminded of myself while I was in really bad depression that lasted 10-15 years on and of, and wanted to suggest you therapy.
I was pleasantly surprised when you mentioned you are already at it.
It helped me immensely, I am happy and life is good now. It took time, first few years until finding good type of therapy and therapist (psychoanalysis was the right one for me, everything else was just not deep enough) and than five years until I got well enough and five more years to heal completely.
Before that I was walking around seeing people laughing and wondering "how can they laugh when world is such a shitty place???"
I wish you good luck and good journey while you get to know and love yourself. You will see there are nice things too, and we humans are wild animals. That's part we fight to repress.
Froyd wrote: "Guilt and the neurotic repression of instinct are simply the price we pay in order to live together harmoniously in families and communities."
It is not easy being nice, it is not our nature. Additionally we are full of trauma that needs healing.