Is Pregnancy Possible Through Precum?

Hi, me and my bf were messing around, im a virgin and so instead of having sex we were grinding, i was on top and sliding along his penis, i was wet so i couldnt tell if any liquid was released but when he got close to cumming we switched so he was away from me. I just learned about pre-cum and so now im scared i could have gotten pregnant. what are the chances, how long do i have to wait before i can check, im supposed to get my period in a week, should i take something before its too late. help please.