Period is late by five days and i feel like it's coming, but its not. could fatigue be just a symptom of sickness?

Illness can cause : Fatigue. Reasons for missed/late periods: low body wt, 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 (polycystic ovary syndrome or asherman’s syndrome). #1 reason is pregnant.