So confused by OPK please help!!

Jessyka
OK, I used digital opks this month starting a few days after AF ended. I got all negatives then on Saturday I got a positive and my bbt went up significantly. We couldn't bd on Saturday so we did on Sunday morning. Then I took another opk Sunday afternoon and it said negative so I guess my lh surge was just in one day...?
 Am I too late? I thought an opk would tell me days before I ovulated so I could really start bd'ing but since I got a negative so quickly after I'm worried I missed my window. Any advice or insight? I've researched a ton and I'm more confused than when I started. 😞😞😞😞