Hi Kath, my diagnosis was similar with a triple neg but my tumour was a little bigger at 1.8cm. I had a lumpectomy, 8 sentinel nodes removed (all clear, clear margins) followed by chemo. I had further surgery later but that was for a different reason.
Is your shoulder pain on the side that your chemo was administered? I only ask because chemo really stuffed up the veins in my arm and I ended up with tendonitis and now a frozen shoulder. Really painful for a long time before the shoulder actually froze - I had excellent range of movement for a long time but now very limited. And because I compensated for it, I have pain in my back as well. Alternatively, this can also happen on the side of surgery, especially when lymph nodes are removed. I would try and see a physio as soon as you can and if this is the case, see if they can loosen up that whole area before it freezes. Early intervention is key if it is the early stages of a frozen shoulder.
The thought of course crossed my mind that maybe the cancer had spread. I think it is only natural to be anxious about this. But this was dismissed by all doctors - clear nodes and margins, a clear bone scan before my treatment. But I still had an ultrasound and xray to see what was going on. The fact that you have an old rotator cuff injury is interesting and again, to me, points towards an early frozen shoulder developing. I would try and see a physio as soon as you can and give them the full story.
Best of luck
Sherril