Maybe they are not doing the test properly...
I tested negative three days before my positive test... The lady at the hospital kept yelling at me for pulling back when she was swabbing my nose cavity... I said, "You're hurting me, it's a natural reflex to pull back when I'm in pain... Are you supposed to be scraping the back of my brain or the nasal cavity???"
She replied that she had to scrape the back of the brain to get an accurate result....
Good luck...
I will think twice before getting tested again after that experience....