I'm 8 days late and have taken a pt and it was neg?

No worries: The menstrual cycle is susceptible to outside influences, so having a late period or missing a single period is rarely of significance. If you miss more than three cycles or 6 months, this is called secondary amenorrhea, the most common cause being pregnancy. Other causes include disorders of the hypothalamus, pituitary, thyroid, ovaries, and uterus.