There are several reasons of missed or delayed period excluding pregnancy
Last time you did protected sex and got period after 3 days and this month no sex.So chance of pregnancy is almost nil. You may clear doubt with urine/blood test
Do a USG lower abdomen and some hormone test (LH/FSH,Thyroid profile etc) to rule out underlying pathology like Ovarian cyst
, Thyroid disorder
,Over wt/Extreme loss, Irregular diet habit,emotional upset may delay your period.
So consult with your gynecologist and take advice according to reports.
Take healthy diet,avoid stress by yoga
,do regular exercise to control body wt and proper sleep.