People who have never coped by harming themselves can't comprehend the effect. For most people their brains tell them to avoid physical pain. For someone under extreme emotions distress you will do anything to not feel the inner turmoil. Self injury isn't a good way to cope. For me every time I did it I felt more guilt and shame and slowly started to hate myself. I found a person that I cared about enough to get me to stop. Therapy helped me as well.
I developed better coping strategies. First I found the things that triggered this behavior. For me it was anything that gave me a sense of rejection, loneliness or when people got angry with me. When I got these feelings I would beat myself up (mentally) over it. Then I would harm myself to stop feeling all the sadness and angry directed towards myself. I would then feel a lot of guilt and shame about what I did, which only added to the feeling of loneliness and angry I directed towards myself. Now when things happen, I objectively look at the events and make a better choices. When someone gets angry with me, it doesn't mean that I am useless and deserve to suffer. It just means they are angry and it's not my fault. I'm allowed to make mistakes and I don't have to be perfect for people to like me. I still feel the urges, but I learned to fight them and I accept hurting myself won't fix the cause of those feeling. I hope this help, I would recommend therapy if you can get some.

Also, I don't think your responsible for your dad's death. You didn't make him sick, and you weren't his nurse. It's natural to think we could have done more. I lost my father when I was 18. He had a heart attack while I was at my uncles house. I always though if I was home that night I could have saved him. There is no guarantee that if you would have stayed anything would be different. It's painful, but it isn't your fault. I hope this makes you feel better.