After I took it, it remained blank. The directions say it takes about 3 minutes to get a result and when I've taken tests before (a few from the same brand, even the same box) the result window starts sliding almost immediately. But this time I continued to glance over at it for about ten minutes and still, nothing was happening. I left it in my bathroom and came back to it about an hour and a half later and it had a negative result (not to mention the directions say it should only stay visible for 30 mins). Should I trust this result?