Tiny craters on shoulders/legs

Since about 2006 I started getting small tiny craters on my skin mainly on my shoulders/arms legs/thighs.
I could never pin point what was happening, I saw it happen before my eyes in the summer when I was just out of the pool there was a small tiny skin type tag and when I wiped it, it came of revealing the tiny crater. I am a high strung person and most of the time I unconciously find myself picking at the scam that forms, which bleeds since the crater was deep. What the heck is this? I was taking massive doses of vitamin C and Stress B complex for my CFS and they seem to really lessen, I didnt take my supplements for a week and they got WORSE!!  I had one on my nose ONE TIME other than that its all lower body, even behind my side ankle, how do they happen? and why? Thank you so much