Dark skin on my privates

You could be dirty. Wash.

It's normal to be black

You could be dying. Good Luck

Skin is rubbing? Are you mixed with multiple races? I am Haitian and Spanish so I am a little light skinned and some of my body is a little, not much, darker.

You could be anaemic. Good luck

You could be diabetic. Go see a doctor. Good luck :-)

...Go see a doctor for these things.