2 days below coverline and brown spotting

I'm looking for opinions. This is my first month charting my bbt. And the past 2 days I've been below my cover line. I took an opk last night and this afternoon and they were both negative. So I am assuming I already ovulated (based on those and my previous positive and temp spike). Today I have had cramping (started last night) like AF is on a really early start (not expected until January 11-13 - 7 to 9 days away). This afternoon I had some brown spotting when I wiped.