I have missed last months and this months period. I have been on birth control pills for over a year and have never missed a pill or taken it at the wrong time. I had unprotected sex, but took several pregnancy tests and all have said negative. Is this normal for an 18 yr old? I'm 5'8" 123lbs. Should I be worried about these missed periods? I still have the cramps, fatigue, and symptoms associated with a period, but show no sign of any lining being sheaded, or "flow."