If the hormones produced during sex change your cycle, then how can a sexually active woman ever have a normal cycle? That makes no sense. I'm not trying to be a jerk, but I don't see how that's logical.
To OP: As it has been said, lots of things can affect your cycle. Is it possible you are pregnant? Yes. Is it possible you are late because you are getting sick or you are stressed out? Yes. Have a test done to confirm one way or another, and then ask your doctor to put you on birth control. If you are going to be sexually active and don't want children right now, it's best to take precautions. Remember though, even being on the pill isn't a 100% guarantee you won't get pregnant, but you will decrease your risk if you use the pill and condoms.
