I have been experiencing this for years and no provider knows why. It never happened with the implanon, only the nexplanon, and when I called to ask them, they said only one ingredient had changed between their two products and I'm probably having a slight reaction. The only odd thing is, is sometimes it happens a lot; daily or weekly, but other times I can go months without it happening. For me it has always been a single bump that starts out small, and if I scratch it it gets bigger, it is almost always directly over the center of the length of the implant. It is happening right now...