Rotten death smell in vagina! Help!

Ok for the past 2 months usually around the end of my period I have this horrible death rotten smell from my vagina discharge. I've been dating the same guy for 2 years and this only happens about a month ago. I thought maybe it was a lost tampon in me buy I stuck my finger all the way up and found noting. What could this be? Is it BV?

Does it stay or go away? I have bv but my odor don't go away

You should go see a gyn.  They can test for bv and yeast.  At least you'll be able to rule those two things out.