What Causes White Spots On The Labia Majora?

Hi please help, I have a tiny cluster of pin prick white spots/blisters on my labia minora on both side, and on the outside where my pubic hairs are growing have raised little white spots. The clusters on the inners lips only aggitate and burn when I have urinated, and touched the area, i thought it might be thrush but i have had thrush before usually with intense itching all the time and alot of discharge so dont think it is that, only ever been sexually active with my husband, and this seems to happen after my period, or sexual activity, what can it be