2 cycles ago I had sore nipples from O day on. If your breast pain is on the sides of your breasts, this indicates that ovulation has occurred, according to Dr. . Sometimes the change comes immediately following O, and sometimes not for a Even had pos opks but didn't actually O until about 5 days later. Find out the six earliest signs of pregnancy here. Some pregnancy symptoms can begin a just few days after conception, even before Next: Breast Changes.