Thanks for your question and concern as you are facing a problem with a disease bacterial vaginosis and yeast infection they both cause itching in the human body at the genitals.In your case there are many chances of infections are their so diagnosis is done on the basis of swab and microscopic study of the area which is affected which is repeated in your case because of the infection that still exists in your problem.

For the prevention and for your asurety there are many ways you can go through which can reduce your risk of infection.As like you can go for the bloodwork for sexually transmitted infection if you think that you are having risk.According to me always go for condom as a precaution which will some how decrease the chance of your  STDs  and I would also suggest you to take your partner tested for STI too.

This will not only ensure you but also ensure about your partner too.So always remember to use condoms and your partner examined for STI.Best wishes