Missed period by 9 days. last period was on 30/12. i did over exercise on 22-24/1, had sex on 25/1. negative pregnancy for 2 times. what could be reas?

Reasons.: If you are not pregnant, other causes of missed or irregular periods include: reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; over-exercising (endurance athletics), travel, significant illnesses, oral contraceptives ; other meds, illegal drug use, breast feeding, hormone imbalances and medical problems.