I've only had this for a year, can i stop myself?

I'm fifteen. :( I do not have any form of natural acne or pimples, but for me i had dry skin on the back of my arms. I just picked at it from annoyance or itch. Unfortunatly, it went from thoughtless removal, to a deep trance like state in which i almost completely blacked out. It was like my body was betraying me, and i was watching it in horror as i made my, as vain as it sounds, pretty porcleian skin into a mess of irritated picked marks. Then, my arms weren't enough. I picked my thighs, the top of my chest, my shoulders, and then i began to do it to my face. I have had this for only a year, and i do not want it to go any further. Thankfully, there is only very faint scars on my arms, everywhere else was shadowed in comparrison to this area for me, but this is a daily struggle for me. I relapse, then i feel horribly depressed. I hate having to constantly pick and choose clothes that hide my self affliction. I hate looking at pictures of myself from last year and seeing how nice my skin COULD be, if only i stopped. But i CANT. i try, and i try, but i fail. As vain as it is, i feel as though i have the potential to be physically pretty, but i just cant get the motive to break my own spell. Im happy with who i am as a person, so why do i do this? I want to stop...or at the very least, reduce this. What should i do? I have had it for a short time, and i am hoping i can catch myself before i ruin my self esteem forever. Only my parents and best friend know, i hide it disgustingly well. But i am not well. Please...i want to stop myself from this, because it's hurting my parents and closest friend...please...