I can understand how hard it is for you to cope.
Can I gently just say this?
I tried to encourage Chris's adult children to do as many things with him as they could.
His son took him fishing ONCE.
11 months after diagnosis and he was gone.
One daughter told me if I wouldn't stop being so negative she wouldn't even come for his birthday dinner (which of course was his last birthday). This was in response to me being disappointed that at the last minute she declined to come and take him out for the day after all and I had cancelled home services. He was gone 3 months later.
My heart broke for them constantly. I was as least as concerned that if they didn't spend time with him while he was mobile and they could understand him speaking (though his speech was the first to be affected), then they would always regret this later.
I wonder if this does play on their minds now, I sure don't ask them as I don't want to seem like I would be accusing them now that I tried to get them involved.
So, what I'm saying is - you are heart broken, I know it, I was also heart broken. You are going through the first stages of grief and shock, be kind to yourself. Find someone to talk to, rant and scream and rage and get that out. Once you are dealing with it, start to think about what can you seriously do to build great memories with your dad while you can.
If he still has several years ahead, you will build a huge stack of them! If not, you will build as many as you can.
These don't have to be elaborate, costly things. But the only thing of value that we have when on our deathbeds are the memories of love and happiness. Bank them up!