it is all quite normal to get pains in your sternum with a sub muscular placement of the implant. Often ones pain improve after a week and one tend to move a little more and sometimes this can cause spasm and hence pain . This will improve over time.
Dear Kadey,The pectoralis muscle is connected to the sternum in the midline. Under the muscle implants cause the muscle to stretch and given this connection to the sternum it is very common to have discomfort there for a couple weeks. Always discuss your symptoms with your surgeon.