8 days past AF and still negative test?? What?

Kacie
So is been 8 days since AF was due according to glow and 14 days according to my calender based on my last period. I don't know why all my tests are negative, should I go get blood work done or just wait it out? Is kind of frustrating because we've been TTC since April 2015. The only thing we did different this last time was we used pre seed.... any advice?