Can Delay In Noriday Contraceptive Intake Lead To Unplanned Pregnancy?

I have been on Noriday for a year. Periods are always around 26 days apart. Last period was 12th March, which was 30 days ago, last time i had sex was the 23rd March. I had painful cramps which felt like period pain a week after the 23rd and have continued to have lighter carmps on and off but no period. Im generally pretty good with noriday but maybe on one occasion may have taken it a few hours late, should this matter? and what are the chances of pregnancy?