Hello-
I have had sore/tender breasts for the last week (sometimes to the point where it hurt to wear a bra). This is not normal for my cycle. Last time this happened to me, turned out I was pregnant. However I did start my cycle today, but the blood is like a dark brown color. Should I be concerned about an infection?

Is it possible you are pregnant? That might be a possibility. Could be the start of your period; some women have a brownish discharge in the beginning. Even if you haven't before, the discharge and sore breasts could be due to your menstrual cycle.

Certainly if you think there is a chance of pregnancy, try a test.

This may be an infection, or also many people have there menstural cycle throughout the pregnancy. Id suggest for you to see your family docter about this, and see what they can do for you.