Worst Experience Ever

WARNING: This story may be disturbing to those who are squeamish. I am 16 years old and have recently discovered that I have dermatillomania. For me, this disorder makes me pick at my scalp almost non-stop. I also bite my nails, so they are very short. This means I have to use 'tools' to pick. Today I was picking with a pair of tweezers at a little spot on my head that is numb to any pain. I shoved one side of the tweezers in and felt them go in between a thick piece of skin and my head. I'm not sure how deep it went in, but I did it again and again, trying to peel that little numb piece of skin off my head. Suddenly blood started rushing out of my head and getting everywhere. I ran to the bathroom and cried out for my mother while watching the blood spatter on the bottom of the sink. I was terrified. My condition had led to me bleeding before, but never this much. My mom came in and helped me, much calmer than I was (I don't know how she does it). It turns out that the head bleeds a lot more than the rest of the body, but even knowing this, I'm still scared. What if it happens again, but in public? What if I can't keep my hands off it the rest of the day. I am so lost. What can I do to resist picking? I can't eliminate all tools because I have to go to school and sometimes I use pencils as picking tools.