hi Dr. i am developing a weird problem. my skin is developing dark patches, behind my knees, on my neck, and in between my thigs, this is embarrassing and i dont know where is this coming from, what could be the problem? i need to deal with this problem internally than just deal with the outer skin, could i be diabetic? basically i dont know if i should go to a Dermatologist or go have tests done(but what tests?)