Hello,
it would help if you could say more specifically do you think that the skin between your thighs and/ or pubic area is darker or if you think specifically about your pubic hair being darker. In both cases this is normal and nothing to be embarassed about. Some women simply do have a bit darker skin in this region and the dermatologist's advice is usually to just leave it be as it is.
The alternatives that are marketed as a 'cure' for this darker skin tone is applying bleaching creams and laser treatments - and that still does not guarantee taht your skin will remain lighter after the expensive treatment is over. Besides, you're still in puberty and your hormones are, so to speak, playing havoc on your whole body. It might very well happen that as you grow older the skin tone normalizes on its own.