SOS!!!

ok so.... someone help. my boyfriend and i bad unprotected sex for the first time yesterday... he didn’t finish, BUT he had earlier that day while he was alone around 12. but precum can pick up old sperm from previous ejaculations, but usually if you pee afterwards, it will carry out most left over sperm. he peed twice since the last time he finished and the time that we did it. we only did it for like 1-2 mins bc his sister got home... awkward lol. but i am supposed to start my period soon, so i feel like this would be the best time for a person to get pregnant.... and with my luck i feel like even with the slim chances of everything, something could happen. i took plan b today around 4pm and this happened yesterday at around 6pm. I should be good right? lmk pls I am soooooo stressed. also should I take a pregnancy test anyways even if I do get my period in about a week? bc my friend got her period at the normal time she was supposed to but was still pregnant.... just to be safe?