ejaculation outside vagina - pregnant ?

hi,i'd like to ask a question.
i had intercourse few days ago (on May 16) but the ejaculation wasn't inside the vagina. it's outside but near the vagina. could i be pregnant because of that?
i haven't had my period yet until now. (it supposed around 18th)
actually,i didn't remember exactly when the last time i got my period,but if i'm not mistaken,the last day of my period was on April 22 or 23. so maybe the first day was around April 17 or 18.
if i take Norlevo,could it prevent pregnancy? but it's already 3days (but more than 72hrs) since the last intercourse.