Lack of menstruation is the first serious sign of pregnancy, but lack of a period can also indicate other conditions. A pregnancy can be confirmed first with a pregnancy test and then via an ultrasound scan. Blood pregnancy tests are more precise than urine-based, HPT home pregnancy tests. Blood-based pregnancy tests are time-limited for accuracy, however. Blood-based pregnancy tests can confirm or exclude pregnancy only in the fist weeks of pregnancy and are not valid after 2 months of pregnancy. You can take a blood pregnancy test, although it seems likely that the test will be negative again. Beside pregnancy, lack of menstruation could be caused by a hormonally active (functional) ovarian cyst. Functional ovarian cysts are typical for women of your reproductive age. Cysts produce hormones that delay a menstrual period and prevent the next round of ovulation. In effect, cysts act like hormonal contraceptive pills. A functional ovarian cyst usually persists for 2-3 months and ends with a heavier “period” with increased blood flow. Ovarian cysts can be seen only via ultrasound scan. You can visit your gynecologist to follow up and request diagnosis.