Need To Vent

My uncle was dianogsed with stage 4 lung cancer in Aug of this year.  We have been very close all my life, he is like my second dad.  The cancer is small cell and has spread to his liver and bones.  He is always on oxygen and is soo weak.  He is has finished his second round of chemo.  I know that things are not good for him, but it is so hard to see him like he is.  I don't know what to say to him. I want to be positive, and try to make him laugh, but it is so hard.  i am so scared that he can see the fear in my eyes.  Last night when I saw him he said that he was so tired of all this sh##.  I keep trying to be upbeat, but seeing him in so much pain is so hard.  I am trying to spend time with him, telling him stories about my little one to make him laugh, and keep his mind off of the pain.  It is so hard to see him like this, he was such a big tough guy and to see him so skinny & weak it about kills me.  Any advice on how to deal with all this?  I am so angry about this, why does he have to suffer like this?  Thanks for letting me vent!!!!!!!!!