What Causes Vaginal Burning During Sex?

Im a 19 year old female. I have vaginal burning during sex only and maybe for several mintues afterwards. I have gotten tested for stds, yeast, vaginosis, and uti but they have all came back clear. the only thing my doctor found was some "bacteria" so she prescribed ciprofloxacin hcl for three days twice daily. i completed the medication and waited a few days but the burning during sex was still present. me and my partner have been together for 2 years, we do not use condoms, and the only other time i have felt burning during sex like this was when i had a yeast infection a couple of months ago. i dont have a lot of discharge and i am very clean as i always shower at least once daily. i don't use douches or use any kind of soap or anything down there. occasionally i will have a sharp pain during sex in my vagina on my right side but my doctor told me with was because of a cyst? and that it was normal, but i have not gotten in thoroughly checked by a gyno. Now that ive listed basically my whole history, what could be wrong with me?