My period suppose to start on 24 July 2014, but I'm not getting anything till 9th August 2014, I had a bad period like pain and dark brown discharge for 3 days (With pain) and now dark brown discharge without any pains. What could be the reason? I did urine pregnancy test on 10th August 2014 and came up negative. No Sexual intercourse (still virgin). What would be the possible reason?

Stress, illness, Germany winning the world cup, PCOS, Thyroid issues, medication, to name a few. How old are you?

What you will learn in life is that your period will be normal and regular 19 times out of 20 (Not an actual number, but expressing the idea of "Most of the Time") and that 20th time you will have something wonky happen. Missing a period, having it late, or early, or heavy, or light, is all part of having it. Largely it isn't something to be concerned with, but if it happens frequently than you should see a doctor about it, but at this point I don't believe it really anything to be concerned with.