My period has been wierd lately, i normally start on the 25th of every month and for the last 3months my periods been changing sep.i started on the 10th than last month i started on the 25th again and this month i was early i started on the 21st can this be a sign of pregnacy? i took a pregnacy test 2weeks after my late period last month and it said no but my period has never been off its always landed on the 25th unless it starts at the beggining of the month? or is it because im 18 and im growing into my woman stage i dont know?