Lower right ab/pelvic pain. worse with moving and sitting up, travles to back. late period not pregnant.

Sounds like: some mild bleeding into the egg remains (called "corpus luteum) Check with your GYN if pain lasts much longer than a few days..or after your period! Hope this helps! Dr Z

Not sure: 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.