Im with Tappa, although Ive never suffered a loss to this affect, I have been depressed and suicidial as far back as I can remember, and most times Im living for others, and sometimes the pain is to much that I feel like I cant go on for anyone. Dont blame yourself, it rarely has anything to do with others, its whats on the inside of the one suffering.
Im so sorry your going through this, my thoughts are with you and family.