As Women, our V is our power but at times can be our headache. Sometimes we don't know what is going on down there and why we are "OFF" at times. Sis its not always us, its the men we let inside of us. Your V is telling you nooooo honey there's too much going on. The alkalinity in Semen can alter out PH Balance which changes the smell. Although after Sex most of the Semen dis out of the V or some try to wash it out as thorough as possible some Semen can remain and cause a change in scent.
So think of it like this; drips of "Brian" are up in there, then drips of "Dave", then drips of "Carl" = off ph balance which can trigger BV. So I recommend Detox pearls and Herbal V Steaming and using an Herbal feminine wash daily to kill bacteria before and after sex. O yea and don't forget to Pee, that's most important after sex !