I have had the nexplanon for about five months now and had no serious issues but for the last three weeks i have had pain in my left breast (the implant is in my left arm). Only my left breast has gotten significantly bigger in size and there is a couple firm spots on the left side. I have been to my Dr. And was told that the cause was from the implant and was just told to put cold compresses and take pain pills. The way i physically feel is more severe to just do what was suggested. I have been trying to get a hold of the fda about this to get more information. I'm also getting another opinion from other doctors.