It's a reaction to the Metronidozole. I had the same thing happen.
I went to the gynecologist 2 weeks ago, she prescribed anti-fungal cream, little ovules to put in my vagina and pills to regulate the yeast but the symptoms are still here, even worse as it now also rectal, I have diabetes and am very stressed at the moment and this does not help!
I think you may need an anti fungal cream as well as the antibiotic. It sounds more like a yeast infection to me hun. I am surprised your physician didn't investigate these symptoms further. All that needs to be done is a culture to see if it is a fungal infection.. It this doesn't clear up by Monday, I would advise you set up a follow up appointment and make these symptoms CLEAR to your GP. I am sorry you are so uncomfortable and in pain hun!
Good luck sweetie!
~VQ