Strange thing happening 😰

Hi 👋 I am having something very strange happening to me. Yesterday, I noticed that on my underwear, instead of white discharge, it was dark brown mixed with deep almost blackish red discharge 😰 It is happening again today and I don't understand what is causing it. I'm a virgin, so I know it doesn't have to do with anything sexual related, and my diet is healthy as well. 
Help? 😥