help a girl out

it seems like I constantly have a yeast infection. I used to think only when I had sex or did things w my bf but I got one 3 days ago and I felt it coming but I hadn't done anything for like a week I think. but why do they keep coming? cures? or is it even a yeast infection? it always goes away w medicine. and I have no stds bc ive only had/have sex w 1 man. and now I feel like my vagina is so raw and burning so bad and it hurts to touch??? someone help a girl out!