Hello, I have gone through your query and understood the concern. There are several possible causes for a delayed period. If pregnancy has been excluded by your doctor, the other possibilities are sudden weight changes, stress, cysts of the ovary and other hormone changes, infections of the pelvic cavity and general infections and use of certain medications. A complete evaluation which includes hormone assays, trans-vaginal sonogram, blood counts and urinalysis along with a proper gynecological exam helps to detect the cause. Please maintain a healthy weight, regular exercise and a healthy diet. Hope this helps.