Is my breast discomfort from a fibroid cyst or could I be pregnant?

I ovulated on November 13th, had sex that night with my husband and he withdrew. 4 days later, both of my breasts began to feel heavy and tender. On November 20th, I noticed that my left breast was larger than my right breast and also much more tender. I felt around and noticed a mass in my breast.
I went to a nurse practitioner today, and she did a breast exam and said she thought I had a fibroid cyst and that I probably wasn't pregnant. I asked her why then did I have tenderness in both of my breasts, since this is abnormal for me. She said it was just hormones.
I am too early to take a home pregnancy test yet. I'll have to wait about one more week. But does anyone have any insight as to why both my breasts would be tender all of the sudden and why this all just came about this month?

BTW, I believe the nurse when she says I probably have a fibroid cyst. I just don't get why both breasts would be tender or why it would start bothering me now all of the sudden.

well if a nurse told you that then i would rely on what she says. if she felt it and examined it best guess is she is right. if you feel like she has came to a wrong diagnosis see another doctor and get a different opinion. pregnancy causes tender breasts i would just wait a while until its time to take a pregnancy test and see if that is the real reason, but I would definetly follow up with the fibroid cyst situation.. good luck and hope you figure this out. : )