Hello Mic1.  So sorry for your loss, I know it is only words, but I know exactly how you feel.  I nursed my Mum when she had terminal cancer, it was almost 30 years ago, but I still miss her.  HOWEVER, I wish to say that eventually, that raw, awful pain you are feeling will subside in to something less painful.  There will come a time when you can think about your Dad and it won't feel like a knife going through your heart.  You will always miss him, but I can promise you that the worst of it will one day pass.  Something that you might wish to consider is grief counselling.  When my cousin lost her Dad (my uncle) she struggled very hard to come to terms with it, and she went for some grief counselling sessions.  She said that it  definitely helped her.  Perhaps you could ask your GP about this?  My thoughts are with you and once again, so sorry for what you are going through.