Tender lumps in muscles – not cancer so what are they

Hi all, I'm hoping one or more of you might have some ideas as to what these might be.  Prior to Easter, I started noticing some tender squishy lumps in my upper arm muscles, back of my upper thighs a back of my shoulders and neck.  They were about the size of a small jelly bean and the consistency of gummy bears which is to say, squishy, not hard.  They seem to come and go (or at least the tenderness does).  I have trouble locating one unless it is tender as they tend to be fairly deep, not right under the skin like a sub q.  I brought them up to my oncologist but of course they were in hiding at that visit.  Being an oncologist, of course he has cancer in mind but I've had two sets of scans since then and these are not showing up.  I now have a few spots on my right side and belly.  More googling has brought up rheumatoid arthritis (I thought that affected joints though not muscles).  Ganglion cyst is another possibility per Google.  I mentioned lipoma and fibroma to my oncologist but he said those don't come and go.  Anyone experience something similar?  Or have some ideas?  My meds are Tafinlar, Mekenist, Keytruda, prednisone, Keppra and Nature-Throid.  I think that's it.  I also take a daily probiotic and vitamin D3.  Any input is appreciated.