Ok My menstrual cycle is every 19days its been this way...for years However, I had unprotected sex Nov 4, 2011 with boyfriend of many yrs..off and on relationshiop I had a menstrual cycle after that, two actually One for November towards the end and the other In Dec. Now My boyfriend and I had broke up I had Protected Intercourse with a friend Dec 22, 2011 I had been off menstrual cycle I believe..3days already before I had sexual intercourse Dec 22, 2011. Now My menstrual came Jan 4, 2012 spotted lightly early that day...Menstrual came down completely Jan 5, 2012 full cycle lasted 8days came off Jan 12, 2012..Now Menstrual came back Jan 18, 2012 Bout 3pm this day...thats a 5day difference and I just came off..and menstrual is trying to leave now as we speak Jan 23, 2012. Why did this occur? I havent had sexual intercourse since Dec 22, 2011 so I'm confused.