Breast Tenderness During Pregnancy
It's very normal. Right before your period it's normal to have tender breasts, too, and it's actually for the same reason: higher levels of the progesterone hormone.
Progesterone levels during pregnancy are even higher than before your period, so you may have even more breast tenderness.
Breasts are at their most tender either before or right around the time you miss your first period. The good news is that the tenderness probably will have eased by the end of your first trimester.