Possible Implantation ? Help!

Kim
Is it possible that I just had implantation bleeding!? I'm 8DPO and I ovulated on day 16 of my cycle and AF isn't suppose to start until Thursday. I've NEVER been 4 days early and didn't even think it was normal to get a period only 8 days after ovulating.  My BBT has remained relatively high and I had a "dip" 3 days ago, but my temp hasn't dipped below the line. 
Any suggestions? I feel like I'm just driving myself crazy and should accept the fact that I probably will start AF in a day.