What Causes White Discoloration On Tip Of Penis Foreskin?

1. my forskin which covers the tip of the pennis is white in color but tip of the pennis is still redish in color 2. if i dont aroused for a weak of so my tip of the forskin becomes very contracted and appears craks and white color but once am aroused the cracks white color disappears. please advise suitabaly i have hustory of frequent musturbation and never had any type of sexual intercorse.