My period is 12 days late. i'm not pregnant. what could be factors causing my extremely late period?

Anything or many thi: If this is your first delay i would not worry about it. May want to seek medical attention if you don't have a period for 3 months. Do a home pregnancy test.

Late: Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems (i.e. PCOS). #1 reason is pregnancy.