Hey, Breast pain and tenderness (especially what you seem to be describing) is an extremely common symptom of a number of things. Interestingly enough, breast pain usually isn't a symptom of of breast cancer in the early stages. Typically the first thing women notice when they develop breast cancer is a lump or abnormality on their breast. These can be detected by doing regular breast self-exams. Instructions on what to do and what to look for can be found here.
More likely, your breast pain is the result of something else. The most common reasons for it are puberty (breasts are more sensitive during this time), menstruation, and muscle soreness for physical exertion in the pectoral area. Pregnancy is also a cause for this, although you only need to consider this if you have been sexually active.
If you are really worried about this, or you think that the pain your experiencing is abnormal, I urge you to go to a doctor and get it checked out. They would be able to tell you if what you're experiencing is normal, or if it's something you should worry about. Additionally, they can perform several tests to check for breast cancer.
If you have any other questions about this, feel free to contact me.
Take care.
-Isobel