Been having vaginal burning after i urinate and vaginal odor and on underwear also a moist brown staining what can it be not sexually active for two years

Bacterial Vaginosis: Knowing you are not preg or sex active helps. This could be a UTI and if so needs to be dx'd and tx't. It could also be bacterial vaginosis, this is an overgrowth of atypical vaginal bacteria which when symptomatic produce a vaginal odor (often described as fishy) and discharge. It is treated with abx & prognosis is good usually causes no probs unless preg. Main other concern would be yeast infect