Besides stress what else can delay a period? i'm 20 days late negative pregnancy tests.

Lots of things can: Delay your period. Low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems. #1 reason is pregnancy. I am assuming that if you are sexually active that you have already taken a home.