What could this mean??

So, AF is due on the 19th. I took a test yesterday and got a big fat negative. For kicks, I took an ovulation test just now, and it came back positive. What the hell does that mean? My peak day was the 6th of this month, we BD'ed for a week straight, including day of peak. I used OPK's when tracking ovulation, and I got quite a few negatives before I hit my peak. Why would I get a positive now?? HELP please!