I have normally got sore nipples for 1 or 2 nights when I ovulate, first month ttc, 4 dpo now and sore nipples since Saturday. Just read this: (anybody experiencing the same thing?)

The Body and The Luteal Phase: With progesterone high, women may experience tender breasts and nipples. Confoundingly, this is also an early pregnancy symptom as well. If you are fertility charting and you know where you are during your cycle, you can dismiss this early tenderness as a possible effect of post-ovulation progesterone. However, if tenderness continues or intensifies when you normally do not experience this sensitivity, you may have an early pregnancy sign. Progesterone can also precipitate PMS-symptoms like irritability, moodiness, etc.