Hello, please do not worry. You took the medication exactly as intended, and your chances of pregnancy right now are extremely low.
Here are the direct answers to your questions:
Is it a safe method? Yes, taking the i-pill within 15 to 20 minutes of unprotected intercourse makes it highly effective, as it is well within the 72-hour window. Furthermore, having intercourse on Day 29 of your cycle means you were likely far past your ovulation window, making your natural risk of pregnancy very low to begin with. However, remember that the i-pill is an emergency backup, not a regular method of birth control.
Does it affect periods? Yes, absolutely. The i-pill contains a very high dose of hormones. Because you took it on Day 29, right when your period was probably due, the sudden spike in hormones will very likely delay your period by a few days to a week. You may also experience some irregular spotting before your actual flow begins.
Next Steps
There is no need to panic. Simply wait for your period to start. Give your body an extra 7 to 10 days to process the hormones. If your period is delayed by more than two weeks, you can take a home
pregnancy test just for your own peace of mind, but the risk remains very low.