What Causes Spreading Out Of Pale White Patches On Buttocks,knee And Thigh?

Two years ago I developed white spots on my buttocks and on the side of my left knee, but I didn t think about them until a month ago when I realized they had spread to my thighs. I than noticed that patches paler than my skin but not as white as the ones on my thighs appear over my torso and and arms . I should mention that I also developed a pale patch on my lip and a tiny white spot on one of my finger. I feared that it was vitiligo and consulted a general physician and a dermatologist. While both assured me that it wasn t vitiligo, as the spors are much paler than my skin but not bright white, neither of them clarified what it was. The GP prescribed a yeast cream and the dermatologist an eczema cream. But nether preformed a wood s lamp test or a biopsy? I am scared that I was misdiagnosed. I thought may be you can provide some clue as to what it is.