My period is now 15 days late & I ve taken 5 pregnancy tests , all are negative but I have symptoms of pregnancy, for eg: exhaustion, backache , Could I be pregnant? I have never missed a period or been more than 2 days late. i have visited a doctor also for the ultra sound but she told me that my endometrium lining is just 3mm and i was 8 days delayed of the period at that time. can some one help me?