Women usually ovulate mid cycle (which is their most fertile time, and when pregnancy can occur). Ovulation determines when you get your period NOT the other way around. So when you ovulate you have around 10-14 (sometimes more) days before your period will begin. Sperm can live in there for around 5 days, so it;s possible that you could conceive from having sex when your did. Since we, nor you, know when you ovulate there is no safe time to have sex and you should then be using condoms at all times if not trying to conceive. All you can do is wait until your next period is due and test with first morning urine if it doesn't show.
generally you ovulate 14days after your period. So i think you may be cutting it close? not for sure but i think ur OK :)