If my period is late, should i be worried about pregnancy?

Depends: Did you have unprotected sex during the past month? If yes, and you are more than 4 days late, do a home pregnancy test. If you are not sexually active, then there is no reason to be concerned.

Potentially: If sexually active - take home pregnancy test. 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