What Causes Dark Circular Marks On The Legs?

Hi, i am 21 years of age and i am having small itchy buttons appearing inbetween my legs and vagina. It has been occuring for the past 2 months. i have done some research on psoriasis and i think i am suffering from it, but i am unsure. After i scratch it, there are dark scaly circular marks remaining. I am really concerned, what do you think i am suffering from?