I am a 21 years old female. Since October 31, 2012 into Novemeber 1, 2012, I have been having a period every 2 weeks and the period was light only lasting a week. On December 10 of this year, I had a period. I was due for my period the week of December 17. My period lasted 2 weeks and it was very heavy. I also suffered from severe abdominal cramps . I am also very tired when I have a period. What does this mean??