I am sorry you are feeling so filled with despair. Psych Central refers people to crisis centers or hotlines that have thoughts of harming themselves or are in danger of doing so.

Here are safety plan explanations and tips so you can devise a plan to prevent self harm.
Psych Central - Search results for Safety plan

If you feel that there is a risk of acting on these thoughts call a hotline right away.

If you have a therapist or psych doc, contact them as soon as you can to look at meds.