It is weird numb pain.Is it a aching, soreness, or sharp pain? Or is it a weird numb pain?
If it's the latter your setup might be way out of wack and you need to review some ergonomics videos.
I read lot about ergonomics of using trackpad
But I have a feeling that because the macbook is tall, it can't be used like this.
I wonder if it could be better with a 14 "Macbook?