Self harm is a way of coping. It is complicated for most people to understand. It is a sign that something is wrong, mostly emmotional, or a mood disorder. Your not a freak and those feelings come from guilt because you know self injury is not healthy. I think you are looking for a way to cope, but you lack the skills. I would reccomend therapy if you can manage it. Also girlofmanyfaces has a good suggestion about keeping a journal. A journal will help you examine why you do it and what you get out if it. Hopefully you can find better resolution to you problems than self harm.

I find self harm to be a cycle. There would be some event that triggered feelings such as inadequatacy or rejection, or personal failure, then I would start to feel depressed, or I would feel intense anger for myself. Then I would get the urge to self harm. I would feel relief or numbness. Then the feeling would return on top of guilt and shame for self harming and I would do it again.