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There are many reasons for delayed periods (menses).
The common ones being ,
If you are sexually active and had unprotected intercourse
then its better to get a urine pregnancy test done to rule out pregnancy even if your periods are just delayed by a week
imbalances due to any changes in weight, diet, perimenopause etc or disorders like PCOD
is very common cause and if you are stressed then it might be the only reason for your delayed periods
A sudden, short illness or even a longer illness can cause your periods to be delayed. This is usually temporary.
5.Changing schedules can really throw off your body clock. This is particularly true if you go from days to nights at work or vice versa.
6.Change in Medications
Perhaps you're trying a new medication and a delayed or absent period is the sideeffect. Be sure to talk to your doctor
about this . It is very common with some methods of birth control too.
So hope you can figure out what is closest to your cause.
In any case if its past another week then do consult your doctor for further evaluation.