I had safe and protected sex 1 month back but i am 5 days late for my period. and i have severe pain in area around my abdomen and below. what must be?

I do not know your : Diagnosis. Severe abdominal pain warrants medical evaluation. 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 med problems. #1 reason is pregnancy.