nicoleb2 has a good point. Chances are that sooner or later, you will go further. Most SI increases in severity over time and can end in accidental death.

What you are feeling is probably endorphins. That is the body's natural "drug of choice". It gives you a "high" when you were previously upset, feeling trapped or depressed. It should never be taken lightly, and should be stopped as soon as possible. What you have done will probablly not leave lasting scars, but if you continue, the scratches will turn into lacerations, and those will.

More important than leaving scars that are embarrassing to explain, you can find yourself in trouble. Infection, permanent disuse of a limb or striking a vessel that leads to dangerous bleeding or even death can easily occur. You might not be trying to cause this, but things get out of control. Without going into details, mine escalated over the years until I came very close to losing a leg. Superficial scratches were my start as well. Get help before you go any further. There is a reason you are turning to this form of behavior, and there are healthier ways of experiencing endorphin release.

You are not a freak, and this is much more common than you think.

Sam2