Late period by 3 days. now having cramping no bleeding. could i be pregnant. or could it be the birth control?

Pregnancy possible: The possibility exists. If you are one week late and still haven't had your menses, you should perform a home pregnancy test.

IT could be from: oral contraceptive. Go ahead and test. 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.