should I take plan b?

I'm on birth control, velivet to be specific. I'm in a long-term manogomous relationship and my boyfriend and I don't use condoms. We had sex Thursday and he finished inside me, Sunday I got diagnosed with bronchitis and got prescribed a z-pack. I know antibiotics can make birth control ineffective and also that sperm can live inside you for up to a week. Is it worth it to take a z-pack? Also my period is supposed to be next week so should I just wait it out?