I'm sorry you are struggling with so much despair.

Honestly I don't have any words of wisdom for you. However here's a link to an "Ask the Therapist" article, from PsychCentral's archives, where therapist Dr. Kristina Randall, Ph.D., LCSW, replies to a question from a person who had struggled with severe depression for 30 years. Perhaps something in Dr. Randall's reply can be of some help:
https://psychcentral.com/ask-the-the...-for-30-years/
My best wishes to you...