Many times Urine Pregnancy Test can be false negative specifically if you have irregular periods and also in cases of delayed conception .it is advisable to do a beta HCG blood test to confirm pregnancy

The result of pregnancy test depends on when it is done and regularity of  your previous menstrual cycles.If your cycles are regular occuring once in 24 to 32 days and test done     1week after your expected date of period,and the urine  for pregnancy test comes negative.,then the cause for delayed period is other than pregnancy. Please get Thyroid funçtion tests, Serum Prolactin and Ultrasound abdomen and pelvis to know the cause of delayed period.

Yes if you are doing through urine chances are there because sometimes false negative result is also there.So confirm by Bhcg .It is blood test and confirmatory also.Negative means no pregnancy then take tablet for withdrawal bleeding.