Breast thickining

I noticed a month ago that my right breast is a bit thicker than the left one in one side not all of it,that is when i self examined them,i also feel some kind of anoynement in the breast area,specialy when my hands are down (i wouldn't call it pain),and this condition becomes clearer when my period is due. I have stopped nursing my baby 4 months ago,but about a week ago i felt that i have fever so i went to the doctor,she checked my breasts and when she squeezed th nipples,an amount of milk came out,she told me that it was the reason,she gave me antibiotic some pills to stop the milk,for a three week treatment. My question is ,is it possible to have this problem even after 4 months of completely stopping the nursing of my baby?why not right away?specially that nothing has changed since i started the treatment,only the fever is gone,but my breast still feels weird,could it be cancer,i'm always afreaid of the mis diagnose?