If you have an infection vaginally, it can throw the delicate balance of good and bad bacteria, which can cause BV or yeast.
Azithromycin doesn't cure BV, so you'll need to talk to your doctor about it, and get a different medication.
Get checked though - don't try to treat yourself. You could have a yeast infection from the azithromycin - it's common to get a yeast infection from antibiotics - and that treatment is different than BV treatment.
I'm sorry this is happening - either yeast or BV sucks.