How Can Bacterial Vaginosis After Sexual Intercourse Be Prevented?

i have had constant cases of BV and i continue to go to the doctor it only comes back after sex protected or not or my menstrual i can not insert anything in my vagina ex tampons, douche etc.. i am taking chewable acidophilus with 90mg lactobacillus acidophilous and 25mg " " bifidus once a day with prenatal vitamins to help with my diet as i seen the smell is very mild and the discharge is normal but it is not gone i have heard of hydrogen proxide and tea tree oil douces and suppositories but i dont believe that this is healthy is there anything i can do? i have used metrogel which has worked for me up until menstural or sex and have spent lost of money of prescriptions for this