Brown Period?

so i today had a brown period, i don't know if its old blood or not, it was like this last month as well but for 5 days. I have changed my schedule alot, i walk to work (15 mins) 3 days a week and do cardio kickboxing 3 days a week. I've drank alot of coffee the last week due to stress. do you know why its brown? i just got out of the shower 2 hours ago and my pad has nothing on it? i am also a virgin