Why My Vagina Is Secreting A Foul Sour Smell Secretion?

feminine issue
for the past few months i've noticed that my vaginal secretions have a very odd scent. its a foul sour smell that gets strong enough that some days i have to wear two pairs of underwear. I don't believe i have a yeast infection (this isn't like the last one i had) and my boyfriend suggested it could be from a UTI but i've had uti's since i was a child and never had that happen before (and i'm currently not experencing any uti symptoms). I'm stumped. any suggestions?