I Had Sex On Thursday (12/11/14) At 10:30 Pm, And

I had sex on Thursday (12/11/14) at 10:30 pm, and had a negative OPK at 5:00 that afternoon. I got a positive OPK (smiley face) on Friday at 4:00 pm and again at 7:30 pm (I did not check on Friday morning). On Saturday morning (8:00 am), my OPK was negative. What are my chances of conceiving? I do not chart, as I was not trying to get pregnant, but using the OPK's for the opposite reason.