Hi Denora,
I am 26 and I am treated for the exact same problem since 5 years.
Since I also have both the bacterial vaginosis and the reoccurring yeast infections, the initial years were a tragedy. Once they treated me with antibiotics against the bacteria, I got the yeast within two month... and the same the other way around.
After a few years a doctor honestly told me that I have this issue, and although these are not serious infections, he can't help me. He said about 4 % of the women have this problem and modern medicine does not know the solution. Its a problem of my imbalance, and he can help me to fix it every time I have bacteria/yeast, but he can not guarantee it will not come back next month.
I am very sad about this issue ever since. What we can do, is aim at some sort of balance. I have tried a lot of things, both for your vaginal and body balance (I don't know why doctors do not care about this...:(), and my problem is more modest now, but has not disappeared. For the vaginal balance you can use intimate products containing lactic acid or lactobacillus, there are such products in pharmacies or you can do it the natural style with yogurt on a tampon (a doctor suggested me that!). But there are a lot of tips even on the internet from using natural underwear and appropriate intimate hygiene that surely help. Also, as the previous comment said we can use inner probiotics, healthy lifestyle, eat less sugar and wheat-flour, do more sports, aim at inner piece... So don't give up, just use less antibiotics, they just make it worse...
And if you find a solution, please share it!
Vera
You might just not have much natural flora in your vagina left. Have you tried taking probiotics?
Also, are you continuing to have sex with the same partner through this, and has that partner been treated at the same time you have? There is a chance of passing things back and forth.