Re-occurring vaginal infection
can be as a result of poor environmental hygiene especially with your underwear, toilet use (public increases risk), and unclean penis just to name a few. So when receiving treatment and after the treatment just make sure that you keep these factors hygienic. Also a vaginal smear + sensitivity can help determine the causative agent and the treatment to be used.
For the whitish powder-like substance during urination, it might be an associated urinary tract infection
with the most like germ being of fungal origin. So urine analysis with indian ink staining should be done.