Defective opk?

I just finished my period from 1/31-2/7. Literally just finished yesterday. I took opk yesterday just for fun because I was on cycle day 8 and got a open circle on clear blue digital. Tonight I took one just for fun because I have been feeling off. Much to my surprise I'm at peak fertility?? Do you think it's just a mistake? We did bd this morning but I had no idea I was ovulating.