There are several reasons of delayed period like hormonal
imbalance, stress/ anxiety, ovarian cyst/ PCOD, thyroid
problem, wt gain/extreme loss, irregular eating habits etc.
I suggest to undergo one blood test
for B-hcg to confirm/ exclude pregnancy
If negative again, some basic investigations should be done like USG lower abdomen, Thyroid profile, LH/FSH etc. So consult with your doctor and take suggestive measures.
Avoid stress,take healthy diet,control body wt and need proper sleep.