What causes bv and yeast infection at the same time? and which should i treat first? i have reoccurring yeast but bv is new to me?

Both BV and vaginal yeast infections are very common, and therefore it isn't rare to have both at once. There may be no particular cause -- but anything that disrupts normal vaginal bacteria can trigger BV. If sexually active, get tested for common STIs like gonorrhea, chlamydia and trichomonas. Do not douche, an unnecessary and unhealthful practice that commonly results in BV.