HI, thanks for using healthcare magic
If you are sexually active and not currently using 
contraception then you should consider a 
pregnancy test.
The home pregnancy tests are accurate and can diagnose pregnancy by day 11 to 14.
If this time has not passed (11 to 14 days), then you should wait a few days before testing.
If this time has passed and the test is negative , then you may need to consider other causes of delayed period.
The other causes of delayed or 
irregular periods are: (1)emotional stress or illness
(2)high levels of 
prolactin hormone
(3)physical illness
(4)abnormal levels of the thyroid hormone
(5)side effect of medication
(6)inadequate diet
(7)polycystic ovarian syndrome
Blood tests and an 
ultrasound are needed to determine if any of the above are present.
I hope this helps