I Have A Itch On My Vagina All The Time

i have a itch on my vagina all the time and a slight burning sensation while having sex. urination is also painful after sex. i do not have any strange discharge or fishy smell. my boyfriend and i have both been tested for stds in the last 6 months and neither of us came back with any. we have not had sex with anyone outside of each other. can you tell me what's wrong with my vagina?