There are several reasons why a woman have delayed menstruation and this could be due to unhealthy diet, stress (emotional or physical), sudden weight gain or loss, caffeine, alcohol, and smoking. Gynecological conditions like polycystic ovarian syndrome (PCOS), and uterine cysts or polyps, can also bring about alteration in menstrual cycle. However, pregnancy is still the most common cause of delayed or missed period.
So if there is a history of any unprotected intercourse then pregnancy should be ruled out.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Hey I am experiencing the same problem. What did you do to fix this problem? I am getting worried.