hello, Most common reason for prolonged delayed period is ovarian cyst or PCOS in the absence of pregnancy. Others are hormonal imbalance, stress, over wt, thyroid problem, high prolactin, irregular diet pattern etc. You need a complete health check up by gynecologist. One pelvic USG and hormone tests are required to pinpoint the diagnosis. Cyclonorm E & P is combined OCP and helps to regularize period. Stomach pain may be due to effect of the pill or acidity/ indigestion problem. However, it will be overcome with time. Maintain a healthy lifestyle. Good luck.