Faint positive followed by negative..

I took two tests on Saturday that very vvfp, however I took one yesterday and this morning- just the strip you dip in urine- and they were negative. I’m waiting for my dr to order lab work. Should I be concerned?! I have so many symptoms and have never had a faint line before. I’m 7 days late today as well. I read a false positive is extremely rare. The second line showed up within a minute of taking both tests too so I know it’s not an evap line..thoughts?