Have you heard of Alien hand syndrome? I was looking up the neuroscience of handedness, particularly the left hand and I came across this, which sounds like it could be what you are dealing with, however I am not a professional and you should always seek the advice of your Neurologist(s) as well as 2nd and 3rd opinions from other doctors. Here is the link.
https://en.wikipedia.org/wiki/Alien_hand_syndrome