What Causes Dark Spots On My Labia Minora?

Hi, I have dark spots on my labia menora I got it once before I went to the dokter and she said it was nothing, and then they disappeared. A few months later (7) I went to my OB/GYN and she check me out and she said I was healthy and clean. But now its been a year and my annual check up is come up in a month and I got the black spots again. And am have panic attacks wondering what it could be. I don't have and other symthomes. Am sexually active but i always use a condom. So help me out .Thx