So you have seen a GP, 2 neurologists and an orthopedic surgeon and you still think you might have ALS?

I am no ALS expert but what you are describing does not sound like ALS.

It sounds like you might have had or had a pinched nerve in your shoulder... The other things might be because you are growing older and are not active. Trust me things state to creep up in your late 30's you never would have thought about earlier in life.

Take a deep breath and find a doctor you trust... Then trust them.

I also would recommend getting active and lifting weights... That way you can maintain muscle mass and actually have a good benchmark for yourself.