I know it's hard but if he's in pain it might be best to euthanize him.

I am so sorry about the unfortunate news, and what you're going through. It's never easy to lose a fur baby, I experienced losing my pal not long ago, I know how hard it can be. I'm sorry OP, nobody deserves to go through what you're going through but just remember your fuzzy buddy isn't having the best of times either. In times like this, just look back upon the wonderful memories you had with him/her, remember, your pal loves you, just as you love them. Spend as much time with them as you can. I wish you and your fur baby the best of luck.

Sorry to hear that OP, I lost the dog I grew up with to cancer too, there was nothing we could do, so we had him put down to end his suffering. Stay strong OP

Ever heard of a mercy kill