Missed period

Okay so I've been tracking my cycles with the clearblue advanced digital. On March 30,31 and August 1 I had the high fertility result (flashing smiley) and then on August 2 I got my positive (solid smiley face). I usually get my period 16 days after, which would have been Thursday/Friday Aug 18 or 19. It's bore Monday and still no period and still negative pregnancy tests. I'm fairly sure of when I ovulated since I was tracking but I'm now confused at my late period. It's been regular with my tracking. Is there still a chance I could be pregnant? I keep testing waiting for a positive and have been getting discouraged not getting one. I think I see a line on some then not on others. I think my eyes are going crazy! Just wanted some input!