13 days late

I'm currently 13 days late. I tested after 8 days without a sign of AF, got a BFN. I'm not trying to conceive but I have been pretty careless with birthcontrol. I have nausea, sore nipples, tiredness, diarrhea and of course no AF. Whether I get a BFN isn't a huge deal, I just want an explanation for AF going MIA. Do you think I should test again at 2 weeks late, go for a blood test or just wait to see if AF comes?