Rash....maybe?

Ok. I have some kind of rash on my vagina and it's itchy. It's on the inside of the "lip". I've been tested for STD's ( gonorrhea syphilis chlamydia, herpes etc.) Within the at 2 months results all negative. Idk if it all started when my SO touched me with unclean hands, but today is day 2 and it has spread from one bump to a small rash. Is this maybe a yeast infection and I should by something over the counter or do I need to see my doctor?