What Causes Extreme Itchiness In The Labia Majora?

hi im 20 years old sexually active and have been tested 3 time for stds and yiest infections all came back negative my pap smear was perfect but a few weeks ago i;ve developed this irritating and annoying itch on my left labia majora theres no discharg eor irritation or burn unless i itch it to its limit theres are one ae two tiny bumpson the surface skin colored barely noticable its like there under the sking help!