The 73-year-old comedian - who was first treated for the early symptoms of the degenerative disorder in mid-2013 - has admitted he gets waves of dark times and has even considered taking his own life to end his crippling suffering, reported Feamlefirst.
Asked if he has ever thought about ending his life, he said: "Yeah sometimes I give it a bit of thought when I'm in bed. I think, 'Well this is forever, this isn't going to get better, it's going to get worse.' But then I try and change my mind and I try and meditate and move away from it sideways.
But the chronic neurological disorder has now started to make the actor drool but he's trying to see the positives.
Billy was diagnosed with Parkinson's three years ago - in the same week he was told he had prostate cancer and had two hearing aids fitted.