So, my period is suppose to start today, but it haven't came on yet and im worried much .. my left breast is tender a lil , but my stomach not bloated?

Know you're worried: 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. If >>.