Metronidazole Help

My doctor has me prescribed metronidazole for my BV she has me taking it 3 times a day for 2 weeks 500mg. And someone just told me for 500mg I should only be taking it twice a day for only 7 days? Could my doctor have made a mistake? I can't call until tomorrow and of course it'll be a wait for her to call me back after I leave a message for her.. I'm 20 weeks pregnant and don't want to harm my baby.