I'm 19, and usually have somewhat regular periods but two months ago it was two weeks late. I thought this was due sickness/the medication I was taking for it, but this time around it has been almost three weeks and no period. I took two pregnancy tests the first time and they were negative, shortly thereafter I got my period...this time I have also taken two tests which have proven to be negative...I still have not gotten my period. Can anyone tell me what might be going on?