What is some reasons why my period is late?

Some reasons: 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 (polycystic ovary syndrome or asherman’s syndrome). #1 reason is pregnancy.

Pregnant or?: 2 reasons to have your period be late: you are pregnant, or your period is delayed because you did not ovulate or ovulated much later than you expected. You could repeat your home pregnancy test in a few days checking your first morning urine or contact your medical provider to see about getting a serum pregnancy test.