Metronidazole and Cyclafem 1/35

Patient: I took a 7 day regimen of Metronidazole to treat Bacterial Vaginosis earlier this month. I am also on Cyclafem 1/35 oral contraceptive which I take on time every day. I recently read that it is important to use another form of contraception for at least 7 days after taking Metronidazole. My boyfriend ejaculated inside me 4 days after taking the antibiotic and while I was taking the oral contraceptive. Should I be worried about pregnancy? Or does this antibiotic not affect birth control as much?

Symptoms: None yet