In the absence of pregnancy
there can be various causs for delay in pregnancy.
The most common causes for delay are
Stress and anxiety
Excessive weight loss
Change in your schedule
Intense exercises like being a dancer or an athlete
After being sick for some time
If you are on certain medications
IN polycystic ovary disorder
disorders etc and the list goes on.
There is nothing to worry for this.Just consult a Gynecologist who will examine you and get you investigated.Pnce the diagnosis is made appropriate medicines can be given and you shall resume your periods.