Pain in left armpit radiating to breast and arm. doc says no swollen glands, no redness. don't feel ill but pain persists. second opinion? infection?

Infection unlikely: Infection anywhere in the body will show signs of inflammation besides pain. Inflammation will produce fever and local tenderness and reddness. In the absence of these signs, infection is unlikely. Pain in the arm can originate in the neck in case there is pressure on the nerves. You should ask your doctor to give you some pain medication and continue to monitor your pain. More tests may be requir.