Why is the time it takes for the contraceptive pills to return to 7 days?

Good morning, On 31.03 I had acute diarrhea and 2 times vomiting - it was almost the end of the second week of Belara contraceptive pills. I take them at 18:00 but at 18:20 I had one visit to the toilet (then I fell asleep until the morning). 01.04 I also had almost birgun until the evening, but after taking the tablet at 18:00 nothing happened. I understand that it was necessary to protect yourself 7 days and the intercourse was on the 7th day, ie the doughnut on April 7. I would like to know why this time is 7 days and if I was already secured