My FR test was done at the same time as yours, two days before my period was due. I thought the test was negative, but I felt pregnant, so I went back and looked again ten minutes later. There was a faint line that really I could only see if I angled it toward the light. I'm 16w today. Just my experience.
I didn't re-test, this is my third, and I knew. Went to my GP about a week later for bloods, etc.