First of all, do a blood test
for beta hcg and ultrasound
scan to exclude pregnancy at the earliest.
In case of both negative test, possible reasons for delayed period are hormonal imbalance, stress/ anxiety, ovarian cyst
, thyroid problem, wt gain/extreme loss,irregular eating habits etc.
Need to investigate properly to rule out underlying pathology by USG lower abdomen,Thyroid profile,LH/FSH etc.So consult with your doctor and take suggestive measures.
Avoid stress,take healthy diet with iron supplements
, control body wt and need proper sleeping.
Practice safe sex by using safe period/OCP/Condom etc to avoid unwanted pregnancy & unnecessary vaginal bleeding. Be well.