Hi gruvingal, I so sorry, I can imagine you're really hurting right now. But try not to hold all of that in, if you can then try to share some of that pain. And remember we're here for you too
Maybe your Dad would be open to conversations, and emotions about how you're feeling??
For some people in that situation they aren't going to want the "pretending things are OK/going to be OK" going on around them "a lot of the time", they're going to want that honesty and that "open doorway" to talk about things inc. feelings and memories/to talk about what might happen and to comfort their children/know that they can make things just a little better for them when/after............
So now might be a good time to talk about things you've shared, things that have been important in your life, memories..............
And if possible maybe plan in some trips to "special" places, places special to you both, or just spend some real time together.
I'm sure you know that time with him is precious anyway, but maybe try to hold onto that knowledge as much as possible, and make the most of it. I know emotions are going to completely ignore that at times but that's natural. And when they do, just know that you can talk about them if/when you want, and if to no-one else, we'll still be here for you.

Alison