Thanks for the answer! I have started a period diary earlier this year, actually. So far though it hasn't been able to predict my periods since I have always been irregular. And yes, after I read your comment I also think that what's happening may be a hormonal change.
Update: I have been getting closer to the color and consistency of discharge that most resembles my normal period. I bled bright red blood quite a bit a while ago. I'm giving it a few hours to see if it goes back to normal now.
It sounds like you just had left over tissue from your last period that did not exit. This old blood would be the first to exit during menstruation. The last few days is usually old blood yet again, but from this period because it did not exit the body fast enough. A 3 day variation is not too uncommon based on your average cycle (seeing as your typical cycle is 32-36 days apart).
Your period may also vary depending on the women you come in contact with. Women tend to "sync" up and this may cause you to get an earlier period.
Brown discharge and irregular periods can be brought upon by hormonal changes, stress, change in diet, or interrupted sleeping patterns. It could also happen due to injury or tearing due to sex. It could also be a number of more serious cases such as polyps, cervical cancer and uterine cancer...ect. If nothing is out of the ordinary, my best guess is that its a hormonal change as you are still young. Start a period diary and if your periods continue to change, go to your gyno with your period diary!
B
honestly, it could be a number of things hun. when your hormones are out of whack, things like this happen.