A little worried

Hi guys, me and my boyfriend on saturday night was fooling around, and we didnt have condoms, we only went in and out for not even 20 seconds, and he dried his cum off his penis before we did, I have taken plan B today 4 days later as I know it can be effective for up to 5 days after unprotected sex, however i am still worried i might be pregnant, how early is too esrly to check just for my own peace of mind. My period is due in two weeks and currently (including saturday) im extremely fertile which is making me worry more.