Hi Caroline, welcome.
That sounds awful! It could be that taking those meds when you didn't need to is making that itching/burning feeling worse. However, I doubt you did any permanent damage, and if you give in another few days, you'll probably be feeling even better. Do you know if they checked for BV? The symptoms are so often the same as a yeast infection, but the treatment's different.
Also, I'd recommend NOT taking a doctor's recommendation unless they're able to see you directly. No matter how well you describe your symptoms, they cannot properly diagnose you without at least looking at you.
Have you tried any kind of anxiety treatment at all? As I'm sure you've gathered by reading this site, things like repeated doctors visits and medical tests actually contribute to worsening anxiety—basically, it's counterproductive, no mater how counterintuitive that sounds.