hello, 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.