Hello,

Thanks for your post. Shooting pain is not a common sign of breast cancer. It may be due to an infection in the armpit (more likely if you shave there), or more likely a deep muscle strain, or trapped nerve.

Try and maintain some gentle stretching exercises, and maybe take some anti-inflammatories such as ibuprofen. Your local pharmacist can advise further. 

Avoid heavy lifting on that side for now, and see if it settles down again. Try and not sleep in an awkward position for your arm. 

You could always make a GP appointment, and cancel it nearer the time if your symptoms improve on their own.

Best wishes,

Vanda