Confused...?

GG
I stopped birth control after my last cycle and haven't had my period yet. I'm 4 days late and have taken multiple pregnancy tests (like..15 of them... lol) and I'm not preg. I just took another test and an ovulation predictor and got a smile on my ovulation predictor?! What the heck? My pregnancy test was negative. What does this mean?! Should I try to conceive with a missed period???