What Causes Tender Breasts Before And After Periods?

okay so i missed two days of cerazettes as i ran out went to doctor and started again then took them fior 3 days but had unprotected sex. I then went to my doctor with the intention of the morning after pill where she look in her medical book and told me as long as i have took 2 (two clear days) i should be protected. So i accepted that as i had 3 clear days and i had also been takin it for over a year. I just had my period and my breasts had got tender before but it finished yesterday and i am still suffereing for tender breasts. But that is the only symptom. I am safe?