If your periods have been regular up to now, then then there may be a chance of pregnancy. However, certain stressors such as excessive exercise or dieting can decrease the frequency of your periods and even stop them altogether.
Urine or blood hCG (human chorionic gonadotropin) tests are routinely ordered 10 or more days after a missed period. The sensitivity of for over the counter urine hCG pregnancy tests varies between 90-97%. Blood hcg tests are more sensitive at 97-99% and they can actually quantify the amount of hCG circulating in the blood. Depending on the test, levels between 20 to 100 mIU/ml of hCG is considered positive for pregnancy. Since you are on birth control – which is unlikely to have any effect on the pregnancy test – if you have had 3 negative pregnancy tests at least 10 days after your missed period, it is unlikely that you are pregnant.
