Trying to prevent BV from returning?

About two weeks ago i went to the Gynocologist because i thought i had some kind of bacterial infection...which i did. She took a sample of the discharge and came back and told me it WAS INDEED a bacterial infection. She never told me which type it was, but im pretty sure it was BV, being that i had every symptom of it. She prescribed me Flagyl (dont know how to spell) twice a day for 7 days. It went away, but now im just worried that its gonna come back..I stopped using fabrics softners with my clothes because washing underwear in it can make it come back..i also try not to eat as much sugar. Im only fifteen, so its not like i can just go change all the food in my house into healthy foods. But i do try to be as healthy as i can be. can yogurt help in preventing my BV from coming back? Bacterial infections are caused when the bad bacteria is growing more than te good bacteria..right? So, would eating yogurt help with the bacteria count? I bought 5 things of yoplait light yougurt. i got strawberry, strawberry banana, and peach. they arent sugar free, becase i didnt see any sugar free yougurt at the store. ive already bought them, so im gonna eat the yougurts....will it work??? also, i cant buy more yogurt everytime i run out, so there might be a few days that ill have to go without it..would tht be ok? or do i have to keep a continuous amount of the yogurt's good bacteria in my system before it will even take effect in helping preventing it?