Pregnancy for me, too.
But, I was on Ortho-Tricyclene for several years after Emily was born, and I complained about breast tenderness from time to time. My midwife told me that it was pretty common with this pill. The pill gives different doses of hormones each week, so it acts similar to how your body would be releasing hormones throughout the month. I can tell you I worried about being pregnancy every time, but I never was.
If you aren't pregnant, the tenderness should go away within a couple of days. If you are, look for it to get like luvmydogs described.
Good luck.
Denae