It is extremely unlikely that you can get pregnant from what you did. Precum does not contain sperm. It comes from a totally different set of glands. It can at most push out left over sperm in his urethra. If he urinated since the last time he ejaculated, this sperm will also be dead.
You can test about 21 days after the sex and repeat it 7 days later. Sooner than that you may get a false negative.
It will also be very unlikely that you are fertile the week before your period. The delay is most likely because of stress and worry.
Best of luck!
Please be very careful when you play.
Well I wasn't worried at all until I started getting weird cramps I thought it was my period but theyve come an gone for the last four days an are kinda different. Also just yesterday we were messing around and he said something feels swollen in my vaginal??? Could that be from my period? I'm so young and know nothing/: