labia minora burn

So one night me and my bf had sex and he ate me out then the next day felt burning thought it was gonna go away then i kinda started to feel itchy a little but only on the top of it not on were i pee then we had sex again but before it was still burning me then we was wet and it would only burn the top of my labia minora but not the sides just that part what can it be ? we both clear from sti and any infection. everytime i wipe myself it burns bad but it does not burn when i pee and also ive had watery white discharge which i think seems to be normal.