I believe hormones from sex can affect your period. I’m not too sure on all the exact details so definitely check out what Dr. Molly has to say for this one. She’ll have a much better answer for you!
There are many things that can affect your cycle — stress, extreme exercise, weight, etc. I'm not sure that sex can actually affect change. Check out Dr. Molly’s answer, I know I'm looking forward to seeing her medical opinion.
Maybe. It isn’t sex exactly that can affect the timing of your period, but rather arousal since that causes a surge in hormones. The mechanics of sex don’t change anything, but if you are aroused (even if you don’t have an orgasm) it causes your hormones to get all jazzed up which can temporarily delay your period. It won’t delay it by much so, if you are late, you should be sure to do a pregnancy test to be on the safe side. Sex won’t make your period irregular though, even if it may delay it by up to a day.
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