Hubby and I are TTC. I took a First Response (line kind) on the first day I could before my missed period. I had a negative test. I am now 4 days late for my period and took the other First Response test in the box. It took almost 10 minutes of painful watching just to get the control line to appear, but hubby and I could not see any hint of another line. I am usually incredibly regular but have not had implantation bleeding although I have had a lot of lower abdominal pressure and mini-cramps the past few days. When I should retest or call the doc about getting a blood test?