Improve taste of vagina?

Apparently my vagina tastes bad as of the last few weeks or so. My boyfriend always said I generally tasted sweet but the last few weeks ive turned sour? It doesnt smell and theres no other real change bar the taste. 
Does anyone have any tips for how i can make it taste better again? Hes becoming relunctant to give oral and I dont blame him! Just want it to be enjoyable for him again too.