What Causes Brownish Vaginal Discharge In A Virgin?

i am 19 years old and im supposed to have my period in 12 to 14 days but i am having a brownish discharge. i have been going to gym for the past 2 weeks and it has been a while since ive exercised so could it be because of that? im having no cramps or anything and the brown discharge amount is not so little like i have to wear a pantyliner and i went to the beach yesterday and tanned for a long time. this is my first day and i am a virgin.