<s>[INST] my girlfriend is a week late for her period and shes taken 3 tests that all have said negative. the first time we had sex she lost her virginity, which was 5 months ago; she was a week late. the second time we have ever had sex was the last time we had sex. which was the last week of last month. why is she late this month? [/INST] Hello dear, i understand your concern. In my opinion the urine pregnancy test gives accurate results a week after missed period. I suggest you to repeat the test after a week. If the test is negative the chances of pregnancy are rare. And wait for spontaneous onset of periods for 10 or 15 days. Sometimes even stress regarding the thought of pregnancy or any other also causes hormonal imbalance which might cause delay or irregular periods. So relax. If there is no spontaneous onset of periods consults gynecologist. If irregular periods continue they need to be evaluated. Best regards... </s>