Vaginal Odor

Ever since I gave birth to my daughter almost two years ago, my vagina has had a nasty smell. It smells of a mixture of ammonia and like something has died in there. My underwear all get stained and look bleached. I've been to my OB, no infections or anything. I am constantly showering or cleaning myself. I'm embarrassed and don't even want my husband anywhere near me because of it. Any idea what it could be? 

Edited: And I was tested/treated a few months back for a yeast infection. If it was any other infection, shouldn't it have been found as well?