I've had this problem for abour 4 - 6 years, every day, every panty, all the time!  This is causing me emotional distress now.  I am embarassed to take my underwear out or even hang them on the washing line to dry.  I feel bad when my husband sees it (he doesn't care about it). He is only concerned for my health.  I replace underwear monthly and throw away the stained ones.  Underwear is expensive! I don't know what to do.