Hi,
Breast pain can be due to many benign causes. Usually the pain occurs due to hormonal fluctuations as it also happens during menstrual cycle and particularly if you are on Hormone Replacement therapy.
I don’t think you should worry about cancer since this disease is almost never associated with pain,especially when both breasts are involved.
Many women actually find relief, when it comes to breast pain, when they cut back on how much caffeine they consume (chocolate, coffee colas).
If you are worried and the pain persists, I consider that a clinical breast exam, preferably by a breast specialist will be the best thing to do to make sure that your breasts are healthy..
I hope you find relief soon and I wish you well.