My period is almost 6 days late, negative pregnancy test? should i take a blood test? what could be going on? usually very regular

Anovulatory cycles: during which an egg is not released, are common and can cause menstrual irregularity or a missed period. Anovulatory cycles are especially common in young women, and 1-2 anovulatory cycles/year is considered normal. Urine pregnancy tests are very reliable and there is not much to be gained by a blood pregnancy test except expense.