My uncle died of pancreatic cancer last summer, and I was pretty close to him. He was like my surrogate father after my real one died when I was ten. I'd been wanting to tell him for a long time and didn't know how he'd react but eventually...I just didn't. I decided that deep down in his heart he knew that I was different and still loved me, even if I never told him and he probably wouldn't understand it fully. He was dying anyway so I figured it wouldn't do much good to tell him since he'd be gone. I'll never know what would have happened had I told him and how he'd react, but my last words to him were "I love you" and I am at peace with that. I still haven't processed his death fully, honestly. Grieving comes when it comes and sometimes it goes away for a while and comes back in full force. It shows up in strange, unrecognizable ways. I used to draw and paint a lot and I just...stopped after his death. I don't know why.
But anyway...I don't have good advice for you. You just have to accept it. Stand by a creek, let the wind blow through your hair. Have the pain in your heart, carry that weight, then get stronger and more able to carry it and let go. There's no easy answers in situations like this. Cancer sucks. I hate cancer. I wish cancer was eradicated from the face of this planet. It's gonna suck. But you'll get through it. It'll be hard. But you'll keep going and eventually it won't be quite as bad. You'll find a way to come to terms with it in your own way and when you're ready.