I've been having an aching pain in my left breast on and off for weeks that has now turned into a throbbing pain that is keeping me awake at night.

See your MD: It is hard to know the cause without more details, but whenever there is a history of ongoing breast pain it is always a wise idea to see your Dr. Whatever the cause is, the therapy is more likely to be successful the sooner it is started instead of delaying it. Pain is your body's warning system that something is wrong, just like a warning light on your car, it is not something you should ignore.