Q: my and this guy had for like 3 minutes, we wore a condom...?

and when we were changing positions i noticed that he precame in the condom so i told him to stop....i made him pull back the condom and it didnt seem to have leakage..this happened a week before my period...if i get my period in a few days does that mean im not pregnant because i kno that if u have while ur body is about to menstruate then u can still be pregnant and get ur period because it was about to come anyway..or do i have to wait until next months period to know for sure???