What Causes Delayed Periods After Losing My Virginity?

hi i lost my virginity the first time 3 weeks ago i was suppost to have my period last week we made sure we were really safe he had a condom and he pulled out way before he was done and we checked the condom after and there was nothing leaking or rips now i haven't had my period yet! would this be because i lost my virginity, because its such a major change in my body? i really need answers cause im freaking out!