2 missed periods.. Need some advice!

Hi all, I've been TTC since December 2015 my last period was January 8th I've missed February period and March period, I've took numerous test all coming back negative I've had one blood test which also came back negative so the doctor thought maybe I could have polycistic ovarys did a blood test for that and it also came back negative. I will now be having a scan within the next two weeks to tell me what's up I've heard people who have had negative blood and urine test and still been pregnant I'm hoping that is the case but probably not.. Anyone else had a similar experience??