Well, it can cause infection, damage the underyling tissues, it produces scars which can hurt for months or even years after they've actually healed, it is addictive, expensive and can cause a lot of embarassment, not to mention discrimination from others.
Is there anything you can try which might be less harmful? there are some great threads on here which suggest different methods you may want to try. A favourite of mine is holding ice cubs in my hands for a really long time, or going for a long walk or run until i can feel my muscles pulsating and aching (this also ensures better sleep which is good for you in the long term).
As i see it, your at a crossroads whereby you can continue with the way things are and end up cutting which could go on for a long time or you can try and take some steps to intervene with your current mindset and change the course of your healing process. Do as much research as you can - get in touch with a health provider in the meantime and possibly get assessed for any illness you may not currently be aware of. Why not jot down your feelings before you cut so you can establish a pattern of what causes you to feel you want to do this to yourself - this may also be a good things to show to a psych if you get referred to one.
Good luck and remember we're always here if you need to talk