12 days late on my period

I am 12 days late on my period; 4 days ago I tested negative. When I had intercourse last night, I bleed a little; but now it stopped. It's not like a normal period where it's flowing. I get my periods regularly every 29-32 day cycle. I am wondering why I bleed a little during sex is because my cervix could be rip or sensitive or a blood vessel might have popped? Or AF is coming? Or I could still be pregnant. I don't want to test until a few days later...any suggestions?