I got my period 2 weeks early, i have some cramps. i did miss a day of pills last week & took tbem at irregular times; is that the cause?

Breakthrough bleed: Breakthrough bleeding (bleeding at the wrong time) is very common on birth control. It happens in about 1/3 of users especially if you are missing pills. If missing pills you may not be adequately protected against pregnancy either. Consider changing to a non daily method like an IUD or Implant for better protection and cycle control.