is possible only, if unprotected sexual intercourse is done with ejaculation around ovulation time in regular period. Ovulation occurs approx 14 days before due date. It is unpredictable in case of irregular period.
First of all, you need to rule out pregnancy by doing one blood test
for beta-HCG at the earliest.
Other reasons for delayed period are hormonal imbalance (most common in this context), stress/ anxiety/ mental upset, ovarian cyst
, irregular diet pattern, wt change, thyroid disorder
Consult with your gynecologist for relevant examination & investigation like USG pelvis, complete hormone profile etc
Avoid stress by regular deep breathing, take healthy diet with iron supplements
, keep bowel regular, control body wt by regular exercise/yoga and take proper sleep.
Be well & take care.