Incapable and irresponsible

I was told that I am incapable and irresponsible. That is true and I was ashamed to realize that.
When I was young, I thought that I will grow up to be a socially desirable person–but I am nothing close to that.
People think that I am a weirdo, outcast. I do not ever hang out with people anymore. I stay home most of the time unless I have to go out for grocery shopping or something.
I cry a lot. Every time I cry, I am in a pain and sadness. and anger. I cannot get used to being alone and crying.
There have been multiple occasions that I was discouraged when I was trying to fit in to society.
The only reason that I must remain alive is my family, my parents and sister. Sometimes I wish that they could see how miserable it is for me to carry this on and start to feel that I would be better off with killing myself and do not exist here anymore as I will no longer be under pressure, stress and fear.
I tried cutting my wrist many times that now I do not do it to kill myself but to calm it down. I wish that I could instead, cut my throat or fire a gun into my head. That way, there is a much higher chance to die and it’s faster. I am not brave enough though. Does this really mean that at the bottom of my heart, I still want to live? It is hard to admit. I feel like a failure again, because I am incapable of carrying this into an action.