Beyond Paranoid

First I like to state that I have OCD (Obsessive Compulsive Disorder), I'm 17 Years Old, and I obsess about everything imaginable. I pretty much pick and scratch every irregularity on my skin. Pimples, Rashes, anything that itches. My underarms itch alot lately.. I think its because of my deorderant, anyway back to the problem... There was this little black thing which I think was a mole that was sticking out of my underarm, and I never saw it before so I think it must have showed up a couple of days ago. Well I was scratching my underarm and I accidently ripped it off, it became a little red where it was ripped off and then got a little better. I told my mother about it and she told me never to do anything like that again because sometimes it could cause cancer. Is this something she told me just to scare me from doing it again because of Scars or is it true? I've been losing sleep over this problem and don't know what to do. I picked at a mole before, one I've had for years and it came of like a layer of skin, a flake maybe. I showed it to my doctor and he said to not worry about it, its normal. I'm naturally tanned, and I never go out in the sun, I live in Arizona where it goes well over the 100 Degree mark. So I stay indoors more then other people. No history of any type of cancer in my family. So am I worry myself over nothing? Or should I have it checked by a Derm. Doctor. It might take a few weeks to get a referal from my normal doctor. So till then I don't know how to keep myself calm. I also sometimes pick things of my back or sides without even knowing what it is, and they easily come off and never bleed or irriatate me again. So does doing this cause cancer, or does it have to be cancer in the first place?