Pregnant?

Okay, so today marks officially 4 days late. Usually, the expected AF days in this app are accurate. So now being 4 days late, it's odd. Took a pregnancy test yesterday morning, came out negative. On the day I was to get AF I had one drop of blood when I wiped after a good hour of some mild cramps. Usually, when AF is to show, I have brown (old blood) first, then INTENSE cramps, then a VERY heavy flow. Since then I've had tiny cramps here and there. No other spotting. Feeling light headed and dizzy at times. Very tired. But that's it. Is it possible that I am still pregnant after getting a BFN yesterday?