I identify very much with your post and so I want to give you some advice.

Don't cut again.

I myself continued to cut after my first time- which was almost identical to yours. I took a pencil with a metal tip and scratched at my arm until it cut, thinking similar thoughts to yours. Now, there are over thirty cuts on each of my arms, fifty on my stomach, and seventy on each of my legs. I can't wear shorts because people will see the scars. I have to be careful to make sure my shirt doesn't ride up, and wear my jacket all the time. When I am sad, because I am so used to cutting, my only way to relieve my pain is by adding more scars. It's painful; both psychically and mentally.

If you need someone to talk to, I am here for you.