Zithromax Z-Pak and gyn

I went to the doctor's office with sinus headache and sinus pressure and pressure in my ears. My doctor tested me and felt I just had a cold. I came back the next day with worse symptoms and a different doctor tested me and she said she felt like I had a cold also, but because it was right before Christmas she will take pity on my and give me Zpak. I started to feel better immediately. It worked great, so I thought. I got a yeast infection from it. My GYN told me to never take that again. And I won't!