I have trouble with birth control and feared the side effects of the IUD. My doctor recommended charting, so three months ago I started charting my bbt and cm. I also use OPK urine strips. I tested positive on CD12 (8.15 PM), CD13 (7:30 PM) and negative on CD14 (today at 1:00 PM). My temperature yesterday was 97.43 and this morning it rose to 97.76. I believe ovulation took place between last night and today before noon. I had intercourse today where my partner ejaculated inside me, but after testing negative. I am not certain if there's a possibility I can still conceive after a negative OPK only hours of a positive OPK. I believe one is said to ovulate 12 -36 hours after a positive OPK.