I would say, symptoms or not, that you have an infection. Some women when they have bacterial vaginosis do not even get symptoms. But, it does make you tender down there. I have never heard of that being a side effect of a b/c pill, but that doesn't mean that it isn't!!
I would go to your doctor and get checked and ask if it maybe is a side effect of the pill you are on. If so, you can switch to a pill that is like yours, but that hopefully will not have that nasty side effect. Hopefully, someone else can help you more!