I had unders Hun, I was expecting not to be able to lift my arms and was shocked I wasn’t in any pain. Like you said just aching and heavy. I’m 5 weeks po and my left sometimes still aches, but my right is fine. They change every day. And I was told to treat them as 2 operation. It’ll will probably be your muscle tightening over your implant. I can remember if I got cold my chest would go very tight and heavy, it’ll be fine once the muscle relaxs and stretches. But if your worried call you nurse. Xx