I haven't had sex for about 6 months and I know stds don't show up for a long time. But I found this circle about the size of a nickel on the skin where my pubes are. It's slightly darker than my regular skin and it looks shiny when I shine a light on it. It doesn't itch nor is it bumpy. It's smooth. Is this an std or is it just a fungal infection that's very common? I'm very worried.