My period is really late but i'm not pregnant ? what can it be?

Many possibilities: Could be stress or hormone imbalance (such as pcos or thyroid disease) or other. Not having a period indicates that the body is sending a message--and figuring out why there's no period is key. You should have some hormone tests done to sort out why you're not having a period. See your dr.

Possible reasons:: Reasons for missed /late periods: low body weight, obesity, marked weight gain or loss, over-exercise such as in endurance athletes, breast-feeding, stress, illness, eating disorders (bulimia or anorexia), travel, hormone irregularities, drug use, medications (i.e., birth control) or med problem (polycystic ovary syndrome or Asherman’s syndrome. #1 reason for missed period is pregnancy.