I'm ruining my life

I'm always so angry at myself. I want so desperatly to stop picking my skin, but even as i'm thinking of this over and over while i'm picking my skin, I can't stop it once i start. it started when I was in 5th grade, just on my arms. However, I'm 17 now and it has spread to every part of my body. It seems like each year I discover a new place that I can completley ruin and disfigure on my body. This next part is really humiliating, but I can't tell anybody and I feel so alone-I just want to know if there is anybody who goes to the extent I do. In the last year I discovered some bumps on my nipples, which I later discovered are normal which many women have. However, I started to try to pop them like pimples, and initially nothing would come out because they are not actually pimples, but after a while I started to actually get whiteheads on my nipples, and now they wont go away, so I keep picking them and I am so ashamed and disgusted with myself. I read this forum and I feel better about picking the rest of my body, but I cannot believe that I actually pick my nipples now. I cant imagine telling anybody, but my friends wonder why I am so self conscious with my boobs and never show them, but if I tell them they would be disgusted, and theres no way they would even think of something like this. Im freaked out because some permanate scarring has already occured and I want to be able to be intimate not only with the person I like right now, but also with anybody else for the rest of my life. My friends think that I dont like them, or dont want to hang out with them a lot, when in reality if i hang out with my friends or not depends entirely on whether or not I have picked my skin to an inch of its life. its summertime and i want to go to the beach with my friends and have summer romance but I am more often than not trapped inside all red and puffy crying and feeling helpless. sometimes i find myself looking at my skin..and then all of the sudden 5 hours have past and i have picked everything until it bleeds and my eyes are blurry from focus. every time i cannot believe what i did to myself and i promise myself i will NEVER pick again..WHY CANT I STOP?! i need serious help.