There are several reasons of delayed period besides pregnancy
. First exclude pregnancy by doing blood test
for beta hcg. Check result and do following if negative again.
Other causes are Ovarian Cyst/PCOD,hormonal imbalance,over wt/extreme loss,stress,emotional upset,eating disorder
,thyroid problem etc.
So do a USG lower abdomen,LH/FSH,Thyroid profile,Blood estrogen & Progesterone
to rule out underlying pathology.
Then consult with your gynecologist and take advice according to test reports.
Control body wt,avoid stress,take healthy diet and sleep properly. Practice safe sex in future to avoid unwanted pregnancy.