I Have One Spot Inside My Vagina That Will Cause

I have one spot inside my vagina that will cause me pain. I have fibromyalgia so it can be painful anyway, so we always use lubricant and plenty of foreplay. It's not every time, it can cause pain right from the start or sometimes in the middle of sex. I have had a Dr. look and nothing could be seen during the exam. The last time we had sex, as soon as that spot started to hurt, it felt like my whole vagina inside set on fire! That was a first time experience. I use a natural supplement called Women's Phase II but have tried a natural hormone creme before and premarin and nothing stops the pain. Could it be a cyst or something and how would a Dr. find it?