Hi Balijo
I think you should be visiting your surgeon to find out what's happened. It sounds a bit like a stitch has popped. My implants move around a bit and I have a noticeable flat area when I lie on my back, but when I'm upright the implants go back to their usual position. My sister, who also had bilateral mastectomies and reconstruction, has had the same experience as you. She has been found to have an empty pocket under her left armpit and the implant has moved in and out of that. Best go and have it checked out.
Hugs,
Jeanine