On pill. Haven't missed one. Had unprotected sex on 14th had cramping since. Period due in 5 days??? What could this be??

See a doctor. Even with perfect usage of birth control. Nothing is 100%. There are other causes of cramping though such as bladder infection, vaginal infection, ovulation, fibroids, unknown causes. If continues or worsens then recommend follow up with a gynecologist.

Related Questions

On pill. Haven't missed one. Had unprotected sex 14th had cramping since. Had period for 3 days but light and quite brown. Neg preg test. What is this?

Probably normal. If your pregnancy test was negative you are likely not pregnant. Women on the pill often experience very light or even absent periods. If you suspect pregnancy please visit your doctor so a test can be done for confirmation.