Jeeees that's rough. My dad died a couple of years ago of lung cancer. The only advice I can give you really is that if there is something you want to do then do it now. Hopefully you'll have a few more years, but by the sounds of your post I'm guessing it's quite short? Well, get on with whatever it is you want to do.
An example: my dad wanted to spend his last few months travelling the world so we gave him as much support as we could.
One good point though, and advice I'll never forget that my dad gave me: he said that it it had given him time to say goodbye to friends and family and get everything in his life sorted out. He said that most people never get that chance but he'd be given that opportunity. He was able to find good in even the bleakest moment. I hope you're able to do the same.
Best of luck. And you're in all our thoughts here.