Scar tissue. Why do I have so much pain on my armpit from the scarring? (Photo)

You appear to have developed a capsule or scar tissue around your implant, and that can be painful. Surgery may be needed to help relieve the problem. There are a few nonsurgical treatments, like external ultrasound, that can be tried first. I would suggest going back to your surgeon to discuss this, or find another surgeon.

The scar tissue could be causing pain along the lateral muscle and the brachial plexus may have compression. Seek a Breast revision specialist for reexamination if pain doesn't resolve!Best of luck 

Thanks fro your question.  Sorry that you are having problems.  From your photo and history, you most likely have significant capsular contracture.  This can make the muscle and breast extremely painful.  The exact cause of your pain is impossible to determine without an examination.  If you do indeed have contracure, surgical removal of the capsule with implant exchange will likely help.  Statistically, there is a higher risk of contracture with a periareolar incision. If you do not feel that your current surgeon is addressing your concerns, a second opinion by a board certified plastic surgeon should be your next step. Online forums will not be able to give you a definitive answer.  Best regards.