Why does it feel so good when I cut my self?

Yester day I intentionaly cut my self like 8 time on my wrist with a pocket knife because I was reall just so depressed I became angry. For like one minute after I did it I felt like I was exctacy! Why does it feel so good? This was the first time Ive ever done it. Im 16. I dont plan on doing it again or anything but it was very strange how good it felt. And the feeling of the blood dripping down my arm was intoxicatingly sensual. Is this bad? Is there a name for something I might have like a disorder or something?