When to start taking birth control pills?

Patient: Hi so i started my period 3 to 4 days ago and i just today got my birth control i was wondering if i can take it today or do i have to wait till my next one to start it but i have a really irregular period so i could miss my next month and i am really worried

Doctor: You can start the birth control pill at any time. If you start within five days after the start of your period, you are protected against pregnancy right away. You will not need to use a backup method of birth control. That means that if your period starts on a Wednesday morning, you can start the pill up to Monday morning to be protected right away. If you start at any other time during your menstrual cycle, you will be protected from pregnancy after seven days. Use another method of birth control like a condom, female condom, diaphragm, or sponge, if you have vaginal intercourse during the first week of use.