Ovulation question. Please help!!!

Kelly • Boymama of 3 💙
I have been opk testing since cd 6. Got a positive reading (smiley face) last night at 530pm on cd12. I tested again this evening to see if I would still get positive reading and it wasn't positive at all. 
​This is  my first month doing opk testing. Is it normal I only get one positive reading a month? I have been testing twice at day (530a and 530p) since cd 6. Here is calendar....do you think I bd enough or should we bd tonight just in case?