Wait a minute - there's no "safe" time of the month when you can have sex without contraception and not risk becoming pregnant. You can also get pregnant:
if you’ve never had a period before,
during your first period, or
after the first time you have sex.
You’re most fertile at the time of ovulation, which usually occurs 12 to 14 days before your next period starts. This is the time of the month when you're most likely to get pregnant.
But there are lots of reasons why it's possible to get pregnant at any time:
your menstrual cycle is not well established and the cycle length might be changed,
sperm can sometimes survive in the female body for up to 6 days.
If you don’t want to become pregnant, please always use contraception.