When is the best time to have a safe sex to avoid pregnancy?
The time you are most likely to get pregnant is about halfway between your last period , when ovulation happens. Ovulation is when an egg is released from the ovaries. BUT following a safe period might just lead to an unwanted pregnancy. This because it's very hard to predict exactly when the egg will be released, random changes occur - trust us! Also females can be fertile for a couple of days before and after ovulation.
If you are having sex it's best to find a reliable birth control method to prevent pregnancy, like the pill or an IUD. And always use condoms to help prevent STIs/STDs.