Can breasts change color when your about to start your period?

A little background: I got my marina taken out on the 15th (last wed) and recently i have been noticing my breasts are turning darker. I haven't had my period or even bleed at all, i've taken 3 pregnancy test and all were negative. I am kind of confused. My husband and i had sex 2 days before i got it taken out not knowing that we could become pregnant. We then did it on fathers day and the day before that. Is it to soon for pregnancy symptoms and am i just starting my period? I haven't had my period for over a year now so my body is kind of out of whack . Serious answers please...