i'm leaking

I was just sitting typing. I was sitting typing and I think that the roof has started leaking because by upper back has become really wet. I don't know what it's from until I turn to look at it after patting the wetness with my fingers. I find that my shoulder is all red and by fingers are sticky because my shoulder is bleeding. I got a scratch on my shoulder today, a tiny scratch, which I thought completely insignificant as it hardly breaks the skin. Next thing I know I'm swamped by blood pouring out of my shoulder as though I've cut an artery. Of course the shoulder being close to the heart the pressure would be high, but my gosh the amount of blood. Sorry for being so biological, but it was a big surprise. I didn't feel anything, I just suddenly realised I was bleeding!