Death is often a topic of over thinking when someone is depressed. Anxiety over those negative topics add to the mix.

Self harm is a way of coping, albeit not a good one. Try to learn to cope by changing your thinking. At the top of the psychotherapy forum is a sticky post about cognitive distortions. It will help you stop that "over thinking" and begin to find the better things of life and living, and find hope for change for you. If you work at it, you'll be carving out an enjoyable life for yourself instead.