Hello, I have gone through your query and understood the concern. Since you have tested negative for pregnancy through the blood test, pregnancy is excluded. The next step is to get a trans-vaginal sonogram to know the status of the pelvic organs and if there are any cysts in the ovary. The menstrual delay could be due to several causes like sudden weight disturbances, stress, infections, hormone imbalances and certain medications. A course of hormones may be given to induce a period if everything is fine as a transient disturbance is often corrected thus. Hope this helps.