Hi. I am 21 years old and have been on and off the pill. (ortho-tricyclen). I cant really remenber the exact date of my last period, I think it was around september 20. And now I have been off the pill since. I have not gotten my period so far. I have some lower back pain and some lower abdominal cramps. Tender breasts started about three days ago, and I thought it was a sign that my period was about to come. I don't feel anything else. Oh, and I took a pregnancy test 2 days ago and it was negative. Should I be worried?