I have missed my period for the past two months, but have taken several pregnancy tests, all of which were negative. I haven't changed anything about my diet, weight, or medications. I recently started a new job and have been stressed, but things have calmed down a great deal recently. Not to mention, I have been in stressful school situations all my life and have never ever missed a period before. Can anyone tell me what might be causing this -- it is really starting to worry me. :(