Could this be an STD? If so, which STD?

Yesterday morning I took a shower and nothing was unusal. Then I got undressed later that night and noticed two pimple looking things on the outside of my vagina. They hurt really bad! The bigger one has grown even bigger since yesterday, and is hurting even more. I looked up genital warts and it doesn't look like that. is this an STD? If so which STD? Also, the last time I had sex was over 8 months ago. (after the first time I had sex I got tested because it was unprotected, no std's then, but then I had sex again a few months later with a different partner but it was with a condom, but I haven't been tested since then)