You have every right to feel low - as I always tell friends, sometimes it's allowed.
I'm sorry things are rough at the moment, it often seems to go this way and I can only reiterate the old saying 'this too will pass' and although no help right now, it is true and eventually all this will be behind you.
In the short term - and this is very small consolation I know - you do have the opportunity to spend time with your Dad and say 'goodbye' properly, saying everything you want to say.
Big hug to you wish I could be more help (((((((((X)))))))))