I'm 70 and a stage III colon cancer survivor. I had surgeries and a long stretch
of chemo. I had some of those symptoms within 4 or 5 years after finishing chemo.
My oncologist told me to expect some good and "not so good" side effects from the
"try to find another doctor"
Let's put aside the term "automimmune" and instead think of "inflammatory disease". What you have should be investigated, not just pushed aside as being all in your head. .
Maybe you have dermatomyositis (unflamed muscles plus a skin condition). That's rare, so docs tend to not consider that. myo = muscles, derma = skin, itis = inflammatory
There are also "idiopathic inflammatory myopathies". The word "idiopathic" means "we don't know what it is and why it happens".
There is "cancer associated myositis".
All those should be ruled out.
"even if low positive it’s still positive"
The doc is correct in saying that low-positive ANA means very little, because a lot of people with no disease still might have low ANA.