What Causes Painful Blisters In Vagina Near Cervix?

My vagina has little blisters near my cervix and i dont know what they are. My boyfriend and i have been checked and have been together for almost 3 years. This just happened and it hurts when i wash. It's happened once before a few months ago and slightly different but the doctor said it could have just been from rough sex. We used different condoms so i dont know if it could be from that or from being a tad dry.