UTI, yeast infection, and BV

I am currently taking nitrofurantoin for a UTI, I have 3 more days on it.

I did a telehealth appointment today to ask for fluconazole so I can prevent a possible yeast infection, because I noticed thick white discharge and have some vaginal burning. The doctor said he would also prescribe metronidazole for BV.

I don't know for sure if I have a yeast infection or BV, so my question is: will it be harmful to take the metronidazole and fluconazole if I don't really know if I have those issues? Or should I just take them to knock everything out just in case? Should I take the metronidazole once I finish the nitrofurantoin, and then take the fluconazole when I'm done with the metronidazole?