Taking Plan B

Missed more than 4 birth control pills and had sex multiple times throughout the week and on my most fertile days. we had no backup method nor did he pull out. its been more than 72 hours since i have had sex unprotected and not sure if i should take Plan B or if it could be dangerous to a possible pregnancy. im in a very long and committed relationship with a very understanding man so im wondering, should i take Plan b or can it cause future issues if i am pregnant since its been 5 days since my first day of unprotected sex?