What Can Explaining Twitching And Pain In Arms And Thumb?

my right arm hurts and my thumb.. if I pick up a cup for too long i have alot of pain in my hand it feels like I cant hold any thing in my hand..my fingers twitch and i feel my right side of my head and veins twitching.. also my arm feels like prssure like when someone is taking your blood pressure.. I had a cat scan and they didnt see anything in my head I'm going to the neurologist tomorrow.. what could be wrong with me?